*  »* 


International  Ctuuatton  j 

EDITED   BY 

WILLIAM  T.  HARRIS,  A.  M.,  LL.  D. 


VOLUME  IV. 


INTERNATIONAL  EDUCATION  SERIES. 

EDITED  BY  W.  T.  HARRIS. 


IT  is  proposed  to  publish,  under  the  above  title,  a  library  for  teachers 
and  school  managers,  and  text-books  for  normal  classes.  The  aim  will 
be  to  provide  works  of  a  useful  practical  character  in  the  broadest  sense. 

The  following  conspectus  will  show  the  ground  to  be  covered  by  the 
series : 

I.— History  Of  Education.  (A.)  Original  systems  as  ex- 
pounded  by  their  founders.  (B.)  Critical  histories  which  set  forth  the 
customs  of  the  past  and  point  out  their  advantages  and  defects,  explain- 
ing the  grounds  of  their  adoption,  and  also  of  their  final  disuse. 

II. — Educational  Criticism.  (A.)  The  noteworthy  arraign- 
ments which  educational  reformers  have  put  forth  against  existing  sys- 
tems :  these  compose  the  classics  of  pedagogy.  (B.)  The  critical  histories 
above  mentioned. 

III.— Systematic  Treatises  on  the  Theory  of  Edu- 
cation. (A.)  Works  written  from  the  historical  standpoint;  these, 
for  the  most  part,  show  a  tendency  to  justify  the  traditional  course  of 
study  and  to  defend  the  prevailing  methods  of  instruction.  (B.)  Works 
written  from  critical  standpoints,  and  to  a  greater  or  less  degree  revolu- 
tionary in  their  tendency. 

IV. — The  Art  Of  Education.  (A.)  Works  on  instruction 
and  discipline,  and  the  practical  details  of  the  school-room.  (B.)  Works 
on  the  organization  and  supervision  of  schools. 

Practical  insight  into  the  educational  methods  in  vogue  can  not  be 
attained  without  a  knowledge  of  the  process  by  which  they  have  come  to 
be  established.  For  this  reason  it  is  proposed  to  give  special  prominence 
to  the  history  of  the  systems  that  have  prevailed. 

Again,  since  history  is  incompetent  to  furnish  the  ideal  of  the  future, 
it  is  necessary  to  devote  large  space  to  works  of  educational  criticism. 
Criticism  is  the  purifying  process  by  which  ideals  are  rendered  clear  and 
potent,  so  that  progress  becomes  possible. 


History  and  criticism  combined  make  possible  a  theory  of  the  whole. 
For,  with  an  ideal  toward  which  the  entire  movement  tends,  and  an  ac- 
count of  the  phases  that  have  appeared  in  time,  the  connected  develop- 
ment of  the  whole  can  be  shown,  and  all  united  into  one  system. 

Lastly,  after  the  science,  comes  the  practice.  The  art  of  education  is 
treated  in  special  works  devoted  to  the  devices  and  technical  details  use- 
ful in  the  school-room. 

It  is  believed  that  the  teacher  does  not  need  authority  so  much  as  in- 
sight in  matters  of  education.  When  he  understands  the  theory  of  edu- 
cation and  the  history  of  its  growth,  and  has  matured  his  own  point 
of  view  by  careful  study  of  the  critical  literature  of  education,  then  he  is 
competent  to  select  or  invent  such  practical  devices  as  are  best  adapted 
to  his  own  wants. 

The  series  will  contain  works  from  European  as  well  as  American 
authors,  and  will  be  under  the  editorship  of  W.  T.  HARRIS,  A.  M.,  LL.  D. 
The  price  for  the  volumes  of  the  series  will  be  $1.60  for  the  larger 
volumes,  76  cents  for  the  smaller  ones. 

Vol.  I.  The  Philosophy  of  Education.  By  Johann  Karl 
Friedrich  Rosenkranz. 

Vol.  II.  A  History  of  Education.  By  Prof.  F.  V.  N.  Painter, 
of  Roanoke,  Virginia. 

VoL  III.  The  Rise  and  Early  Constitution  of  Univer- 
sities. With  a  Survey  of  Mediaeval  Education.  By  S.  S.  Laurie, 
LL.  D.,  Professor  of  the  Institutes  and  History  of  Education  in  the 
University  of  Edinburgh. 


INTERNATIONAL  EDUCATION  SERIES 


THE 


VENTILATION  AND  WARMING  OF 
SCHOOL  BUILDINGS 


BY 

GILBERT  B.   MORRISON 

TEACHER  OF   PUY81C8  AND  CHEMISTRY  IN  KANSAS  CITY  HIGH-SCHOOL 


NEW  YORK 
D.    APPLETON    AND    COMPANY 

1887 


COPYRIGHT,  1887, 
BY  D.  APPLETON  AND  COMPANY. 


EDITOR'S   PEEFAOE. 


THE  practical  character  of  the  present  volume  will 
be  at  once  manifest.  Of  the  four  departments  of  edu- 
cational literature — history,  criticism,  theory,  and  prac- 
tice— the  last  includes  two  classes  of  works :  . 

1.  Those  that  relate  to  instruction  and  discipline, 
and  the  details  of  teaching.     Under  this  head  come  the 
arrangement  of  the  course  of  study,  the  programme  of 
daily  work,  the  methods  of  teaching  and  discipline. 

2.  Those  that  relate  to  the  organization  and  super- 
vision of  schools.     Under  this  head  we  include  works 
relating  to  school  legislation,   governing  boards,   the 
building  of  school-houses,  and  the  organization  of  a 
corps  of  teachers. 

Of  these  practical  matters — practical  because  they 
relate  to  the  application  of  theory  to  details,  and  imply 
the  adaptation  of  means  to  ends — the  question  of  the 
proper  construction  of  school-houses  is  justly  esteemed 
to  be  of  great  importance.  The  school-house  is  a  per- 
manent affair.  Other  matters  may  be  changed  with  less 
ceremony ;  a  building  stands  for  two  or  more  genera- 
tions. If  it  is  faulty  in  its  method  of  lighting,  it  will 
send  out  every  seven  years  its  quota  of  children  all 


yi  EDITOR'S  PREFACE. 

affected  more  or  less  with  a  tendency  to  weakness  of 
eyes,  near-sightedness,  and  to  nervous  dyspepsia  and 
irritability  of  temper.  If  the  ventilation  has  been  de- 
fective, and  a  remedy  has  been  sought  by  opening  the 
windows,  so  as  to  admit  cold  air  from  the  bottom,  the 
seeds  of  future  rheumatism  and  heart-disease  have 
been  sowed.  If  the  warming  has  been  imperfect,  a 
long  series  of  colds  have  weakened  the  lungs  of  pupils, 
and  many  cases  of  consumption  resulted. 

The  author  truly  remarks  that  "  the  greatest  necessi- 
ties are  often  not  felt  as  wants."  Our  early  experience 
in  a  school-room  that  failed  in  these  essential  particu- 
lars has  left  on  our  minds,  perhaps,  in  most  cases,  the 
impression  that  we  did  very  well  in  the  old-fashioned 
school-house.  We  were  not  able  then  to  trace  causes 
and  effects  in  these  matters  on  account  of  ignorance  of 
hygiene.  We  have  seen  evil  enough  befall  our  com- 
panions in  their  life  subsequent  to  the  school,  but  it  has 
not  occurred  to  us  to  trace  it  to  the  exposure  incident 
to  improperly  constructed  school-buildings. 

It  is  believed  that  the  present  work  furnishes  a  good 
text-book  and  book  of  reference  to  be  used  in  normal 
institutes  and  normal  schools.  A  short  course  of  lessons 
or  lectures  will  suffice  to  qualify  a  teacher  to  judge  cor- 
rectly in  matters  of  ventilation,  and  to  act  efficiently 
under  all  circumstances.  When  this  is  considered,  it 
will  be  seen  that  every  corps  of  teachers  should  be 
taught  the  theory  and  practice  of  warming  and  ven- 
tilating according  to  the  experimental  or  investigating 
method. 

I  have  drawn  up  the  following  syllabus  of  topics 
and  suggestions  for  a  course  of  eight  lessons,  covering 


EDITOR'S  PREFACE.  yii 

the  most  important  items  of  the  subject.  I  have  also 
added  a  full  analysis  of  the  contents  of  the  volume : 

LESSON  I. — The  general  principles  of  hygiene  as  re- 
lated to  ventilation.  The  necessity  of  pure  air.  Analy- 
sis of  air.  What  impurities  are  found  in  the  air  of 
un ventilated  school-rooms.  Pasteur's  experiments.  Ef- 
fect of  breathing  impure  air — stupor,  headaches,  diseases 
of  the  lungs,  dyspepsia,  nervous  affections,  etc.  (Chap- 
ters I,  H,  III). 

LESSON  II. — How  to  test  the  purity  of  the  air  (Chap- 
ter IV).  The  proper  degree  of  moisture  in  the  air — 
73  per  cent  of  saturation  (Chapter  III).  How  to  test 
the  degree  of  humidity  (Appendix  A,  page  161,  Glai- 
sher's  factors).  Amounts  of  moisture  in  the  out-door 
air  at  different  temperatures  (page  162) :  at  80°  Fahr., 
elastic  force  1-023 ;  at  70°,  '733 ;  at  50°,  -361 ;  at  32°, 
•181 ;  at  20°,  -108 ;  at  zero,  -OM.  If  out-door  air  at  a 
temperature  of  20°  Fahr.  is  heated  in  the  school-room  to 
70°  without  adding  moisture  to  it,  it  is  seven  times  as 
dry — that  is  to  say,  its  capacity  to  absorb  moisture  has 
become  seven  times  as  great  as  before.  Hence  the  dele- 
terious effect  on  the  mucous  membrane  of  the  air-pas- 
sages and  even  on  the  skin  of  the  body. 

LESSON  III. — The  proper  amount  of  light  for  a 
school-room.  It  should  be  lighted  on  two  sides — from 
the  rear  of  the  pupils  and  from  the  left-hand  side — not 
from  the  right-hand  side,  because  of  the  shadow  of  the 
hand  upon  the  paper  when  writing  or  drawing.  The 
windows  should  extend  to  the  top  of  the  room,  or  at 
least  as  high  as  one  half  the  width  of  the  room,  in  order 
to  light  sufficiently  the  pupils  sitting  farthest  from  the 
windows.  Hence  the  room  should  not  be  too  wide — 


EDITOR'S  PREFACE. 

not  over  24  or  28  feet  when  the  windows  extend  14  feet 
above  the  floor.  The  length  of  the  room  may  be  32  or 
34  feet.  There  should  be  three  windows  on  the  side  and 
two  at  the  end  of  the  room.  Double  windows  are  very 
desirable  for  ventilation  purposes  (Chapter  X),  and  for 
protection  in  very  cold  weather,  when  a  current  of 
chilled  air  falls  down  the  surface  of  the  window.  If  a 
room  happens  to  be  seated  so  that  light  comes  from  the 
right  hand  of  the  pupil,  the  desks  may  be  changed  so 
as  to  bring  it  from  the  left  hand  and  rear.  A  school- 
building  is  ill  constructed  if  its  rooms  have  windows  on 
one  side  only,  unless  the  rooms  are  very  narrow,  and 
receive  light  solely  from  the  north,  as  such  rooms  are 
sometimes  constructed  in  Europe  for  advantages  in 
drawing-lessons.  Rooms  on  the  south,  east,  or  west  side 
of  the  building  must  exclude  the  direct  rays  of  the  sun 
during  some  portion  of  the  day  by  curtains  or  shutters, 
and  the  consequence  is  that  pupils  sitting  remote  from 
the  windows  get  too  little  light,  unless  thin  white  cur- 
tains are  used  and  the  windows  are  very  large,  and  in 
height  equal  to  two  thirds  the  width  of  the  room. 
Pupils  sitting  in  twilight  (the  shutters  being  closed) 
become  near-sighted  in  consequence  of  straining  their 
eyes,  or  because  they  acquire  a  habit  of  holding  the 
book  too  near  the  eyes.  The  correct  form  of  school- 
building  requires  four  rooms  to  each  story —one  on  each 
corner.  Two  or  three  stories  at  most  is  enough,  and  a 
school-house  should  not  stand  nearer  than  70  feet  to 
another  building,  on  account  of  the  obstruction  to  light 
occasioned  by  it,  especially  to  the  rooms  of  the  ground 
story. 

LESSON  IV. — The  amount  of  air  required  per  pupil 


EDITOR'S  PREFACE. 


IX 


— 2,000  feet  per  hour  (Chapter  Y).  The  average  school- 
room, 28  x  34  x  14,  with  50  pupils,  furnishes  fresh  air 
enough  to  last  7  minutes.  Methods  of  calculating 
the  size  of  ventilators  necessary,  and  the  rapidity  of  the 
movement  of  the  currents  of  air  admitted  through 
them  (Chapter  V).  The  registers  for  the  entrance  of 
fresh  air  properly  warmed  should  be  distributed  around 
the  room.  Natural  ventilation  depends  on  the  fact  that 
heated  air  is  lighter  and  rises ;  passing  out  of  the  top 
of  the  room,  it  sucks  in  fresh  air  through  the  inlets 
below  (Chapters  V  and  YI).  The  inlets  should  be 
placed  near  the  floor.  Why  2  (Chapter  YII.)  Size  of 
flues  admitting  fresh  air  for  75  children — 10  square 
feet  of  total  area.  The  foul-air  flues  should  have  an 
equal  area.  Importance  of  frequent  cleaning  of  the 
foul-air  shafts  (Chapter  YIII). 

LESSON  Y. — Aspirating  chimneys — what  they  are, 
and  how  large.  The  velocity  of  the  column  of  air  as- 
cending to  be  7'7  feet  per  second.  Discuss  the  two 
methods :  (a)  Drawing  the  foul  air  out  of  the  bottom  of 
the  room  into  the  aspirating  chimney ;  (J)  out  of  the 
top  of  the  room  (Chapter  IX).  The  theory  that  im- 
pure air  falls  to  the  floor  incorrect  (Chapter  YII). 
Method  of  drawing  down  pure  air  through  a  ventilating 
shaft.  Necessity  of  heating  the  column  of  air  in  a  foul- 
air  shaft  to  secure  its  efficient  movement.  The  best 
plan  to  build  large  aspirating  chimneys  with  iron  smoke- 
stacks passing  up  through  the  center  to  heat  the  foul 
air. 

LESSON  VI. — Ventilation  by  windows  (Chapter  X). 
Inconveniences  of  such  ventilation — dust,  smoke,  waste 
of  heat,  cold  drafts,  etc.  On  account  of  defective  plans 


x  EDITOR'S  PREFACE. 

for  school-buildings,  99  per  cent  of  the  school-houses 
depend  on  windows  and  doors  for  ventilation.  Always 
lower  the  windows  from  the  top,  except  when  the  out- 
door temperature  is  above  80°  Fahr.,  when  they  may 
be  also  raised  from  the  bottom.  In  very  cold  or  windy 
weather  the  windows  should  be  lowered  only  one  inch, 
or  even  less ;  in  moderate  weather  12  inches,  or  even 
more.  But  all  windows  should  be  lowered  alike,  so  as 
to  move  all  the  air  in  the  room ;  otherwise  the  ventila- 
tion will  be  very  imperfect.  If  a  window  is  opened 
too  wide  in  cold  weather,  a  chilly  current  pours  in 
upon  the  necks  and  shoulders  of  children,  and  produces 
colds  or  rheumatism.  If  the  windows  are  lowered  only 
slightly,  the  cold  fresh  air  moves  down  the  surface  of 
the  wall  and  gets  warmed  somewhat  in  its  descent  by 
contact,  with  the  heated  air.  The  devices  of  oblique 
boards  fastened  to  the  sash  (Chapter  X).  The  effects 
of  the  wind  when  strong  sometimes  require  the  windows 
on  one  side  to  be  nearly  or  quite  closed. 

LESSON  YII. — The  most  efficient  means  of  ventilat- 
ing is  a  fan  or  blower  (Chapter  XII).  It  should  be 
placed  in  the  flues  for  fresh  warm  air  (plenum  move- 
ment), and  not  in  the  impure-air  shaft  (vacuum  move- 
ment) (pages  79  and  80).  The  action  of  Bittenger's 
fan  (pages  84^87  and  Appendix  C) ;  of  the  Blackman 
fan  (Appendix  F).  The  method  of  calculating  the 
efficiency  of  the  aspirating  chimney  (Chapter  XI  and 
Appendix  B). 

LESSON  YIII. — The  proper  temperature  of  a  room, 
70°  Fahr.  (Chapter  XVI).  General  methods  of  warm- 
ing :  conduction,  i.  e.,  by  stove-pipes ;  convection,  i.  e., 
by  hot  air  from  furnace  or  steam-coil ;  radiation,  i.  e., 


EDITOR'S  PREFACE.  xi 

by  open  fire-place,  standing  coil,  or  stove.  Importance 
of  using  large  stoves  or  furnaces  to  "avoid  the  neces- 
sity of  overheating.  The  poisonous  gases  that  escape 
through  iron  when  heated  to  redness.  Great  advantage 
of  radiant  heat.  Nearest  to  solar  heat.  Dr.  Arnott's 
smokeless  grate ;  open  fireplaces  (Chapter  XYII).  The 
Ruttan  system.  Advantages  and  disadvantages  of  steam 
heating  (Chapter  XVIII).  Direct  radiation  from  steam- 
coils  not  good  for  the  school-room,  because  it  does  not 
provide  for  moving  the  air  of  the  room  and  for  supply- 
ing fresh  air ;  warms  the  same  air  over  and  over ;  diffi- 
cult to  provide  for  moistening  the  air ;  needs  a  ventilat- 
ing fan  to  render  it  efficient.  Prof.  Morrison's  ideal 
plan  for  warming  and  ventilating ;  distributes  his  steam- 
coils  underneath  the  floor  with  many  small  registers 
opening  into  the  aisles  of  the  school-room;  foul  air 
escapes  at  the  top  of  the  room  into  an  aspirating  chim- 
ney. 


CONTENTS. 


CHAP.  PAOB 

I. — NEEDED  INFORMATION 11 

II. — THE  EFFECTS  OF  BREATHING  IMPURE  AIR         .        .        .17 

III.— THE  AIR 24 

IV. — EXAMINATION  OF  THE  AIR 31 

V. — AMOUNT  OF  AIR  REQUIRED 38 

VI. — GENERAL  PRINCIPLES  OF  VENTILATION     ....      45 

VII. — NATURAL  VENTILATION 48 

VIII.— INLETS 61 

IX. — REGULATING  THE  DRAFT  OF  OPENINGS— THE  WIND.        •       56 

X. — VENTILATION  BY  WINDOWS 62 

XL — ARTIFICIAL  VENTILATION 70 

XII. — THE  MOVEMENT  OF  THE  AIR  BY  MECHANICAL  MEANS       .      78 

XIII. — AIR-PROPELLERS 82 

XIV. — CAN  THE  PLENUM  MOVEMENT  BE  AFFORDED  ?  .        .        ,90 

XV. — THE  COST  or  VENTILATION 97 

XVI.— WARMING .        .104 

XVII. — METHODS  OF  WARMING Ill 

XVIII.— STEAM  HEATING 129 

XIX. — AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING  .        .     144 
APPENDIX  A. — METHOD  OF  TESTING  THE  HUMIDITY  OF  THE  AIR     .     160 

B. — ASPIRATING  CHIMNEYS 163 

C. — RITTENGER'S  FAN  (page  84) 166 

D. — CONDUCTING  POWER  OF  MATERIAL  .  .  .  .167 
E. — RADIATING  AND  ABSORBING  POWER  OF  MATERIALS  .  168 
F.— THE  BLACKMAN  FAN  169 


ANALYSIS  OF  CONTENTS. 


CHAPTER  I.  Needed  Information. — Advice  plentiful  (p.  11);  questions 
to  be  answered  regarding  impure  air — where  found,  its  causes,  its  reme- 
dies ;  most  of  the  school-houses  in  the  United  States  made  without  atten- 
tion to  ventilation  (p.  12);  they  depend  on  loose-fitting  windows  and 
doors  for  fresh  air ;  report  of  the  commission  appointed  by  Congress  on 
the  public-school  buildings  in  the  District  of  Columbia  (p.  13) ;  systems 
of  warming  and  ventilating  in  Boston,  Denver,  London,  Vienna  (p.  14) ; 
authorities  consulted,  R.  S.  Roeschlaub,  Professors  Parkes  and  Draper, 
Dr.  de  Chaumont,  General  Moran ;  Dr.  Neil  Arnott  (p.  15)  and  his  la- 
bors (p.  16). 

CHAPTER  II.  The  Effects  of  Breathing  Impure  Air. — Symptoms  caused 
by  breathing  impure  air;  stupor, headache,  etc.  (p.  17);  not  the  carbonic 
dioxide,  but  the  poisonous  emanations  from  the  skin  and  lungs  (p.  18); 
bad  air  the  cause  of  consumption ;  authorities  and  statistics ;  ventilation  on 
ships ;  New  York  Board  of  Health  attributes  40  per  cent  of  all  deaths  to 
breathing  impure  air  (p.  21)  ;  effect  of  bad  air  on  the  work  of  the  pupils 
and  on  their  behavior  (p.  22) ;  financial  waste  in  neglecting  ventilation 
(p.  23). 

CHAPTEB  III.  The  Air. — Its  composition :  contains  carbonic  dioxide, 
even  in  its  pure  state,  one  part  in  2,600  (p.  24).  Its  impurities:  their  di- 
lution in  the  air,  diffusion ;  ammonia  the  great  supporter  of  microscopic 
animals,  200  forms  of  them  found  in  the  air ;  Koch's  and  Pasteur's  ex- 
periments (p.  26) ;  street-dust  near  the  ground  contained  45  per  cent  of 
organic  matter  and  30  per  cent  at  a  height  of  134  feet;  ground  air 
unwholesome;  air  poisoned  by  stoves  and  heating  apparatus  (p.  27). 
Humidity  of  the  air:  importance  of  supplying  moisture  to  air  heated 
in  cold  weather ;  the  dew-point ;  73  per  cent  of  saturation  the  healthy 
standard ;  statistics  in  hospitals,  Washington  and  Boston ;  shallow  vcs- 


XVI  ANALYSIS  OF  CONTENTS. 

sels  of  water  on  stoves  and  heating  coils  or  hot-air  ducts  (p.  30) ;  hy- 
grometers. 

CHAPTER  IV.  Examination  of  the  Air. — Microscopic:  Woulfe's  bottles 
of  pure  distilled  water  connected  by  tubes  and  an  air-pump  (p.  32) ;  cul- 
tivating solution.  Chemical:  tests  for  carbonic  dioxide,  (pp.  33-37). 

CHAPTER  V.  Amount  of  Air  required, — One  person  evolves  from  0'4 
to  0'7  of  a  cubic  foot  of  carbonic  dioxide  in  an  hour,  and  vitiates  2,000 
to  3,500  cubic  feet  of  air  per  hour  (p.  39) ;  a  school-room  of  average  size 
(28  x  34  x  14  feet)  would  supply  fresh  air  for  less  than  seven  minutes  if 
there  were  no  means  of  ventilation ;  how  to  estimate  the  amount  of  air 
passing  through  a  room  (p.  40) ;  air  rushes  into  a  vacuum  with  a  velocity 
equal  to  what  a  body  acquires  in  falling  five  miles ;  it  rushes  into  a 
room  through  a  ventilator  at  a  velocity  equal  to  eight  times  the  square  root 
of  the  height  of  the  exit  orifice  multiplied  by  the  difference  between  the 
out-door  and  in-door  temperatures  in  degrees  Fahr.  and  divided  by  4  91  (p. 
42) ;  the  anemometer  can  measure  this ;  insufficiency  of  ventilating 
registers  and  flues  ordinarily  in  use  (p.  44) ;  air  should  be  distributed  to 
all  parts  of  room  through  many  registers. 

CHAPTER  VI.  General  Principles  of  Ventilation. — Natural  ventilation 
secured  through  the  tendency  of  heated  air  to  rise ;  artificial  ventilation 
secured  by  mechanical  power  •  illustration  (p.  47). 

CHAPTER  VII.  Natural  Ventilation. — Ventilators  should  be  at  the 
top  of  the  room  (p.  48) ;  foul  air  rises  with  the  heated  air  and  is  not  to 
be  found  at  the  bottom  of  the  room ;  Mr.  Leeds's  experiment  not  conclu- 
sive (p.  60). 

CHAPTER  VIII.  Inlets. — Should  be  placed  near  the  floor ;  but  avoid 
cold  drafts ;  warm  the  air  before  admitting  it  to  the  room ;  downward 
currents  in  summer;  the  inlets  for  air  for  75  children  should  have  an 
area  of  10  square  feet,  and  there  should  be  the  same  area  to  the  outlet 
flues,  where  there  is  a  good  aspirating  chimney  giving  a  velocity  of  7'7 
feet  per  second  ;  the  inlets  should  always  be  distributed  round  the  room, 
so  that  free  diffusion  may  occur ;  the  air  furnished  from  a  pure  source 
and  drawn  from  some  distance  above  the  ground  (p.  54) ;  shapes  of  cowls 
or  conical  caps  to  the  shafts ;  shafts  frequently  cleaned  (p.  56). 

CHAPTER  IX.  Regulating  the  Draft  of  Openings — the  Wind. — The  ac- 
tion of  the  wind  modifies  the  results  obtained :  increases  the  pressure  of 
the  air  on  the  windward  side  of  the  room  ;  measurement  of  its  amount 
(p.  57) ;  classification  of  winds ;  Dr.  Arnott's  current-regulating  air-valve 
(p.  58) ;  admission  of  air  at  the  top  of  the  room ;  McKinnell's  circular 
tube  (p.  61). 


ANALYSIS  OF  CONTENTS.  xvii 

CHAPTER  X.  Ventilation  by  Windows. — Primary  office  of  windows  to 
admit  light ;  secondary  office  to  ventilate ;  the  best  ventilators  in  sum- 
mer ;  admit  dust  and  smoke ;  deflection  of  currents  admitted  by  means 
of  oblique  boards  fastened  to  the  sash  (p.  64) ;  method  of  opening  win- 
dows when  the  wind  is  blowing  in  order  to  secure  fresh  air  without  drafts 
(p.  66) ;  the  best  results  secured  by  double  windows  (p.  68). 

CHAPTER  XI.  Artificial  Ventilation. — The  vacuum  movement — aspi- 
rating chimneys ;  a  column  of  heated  air  moves  up  the  chimney  and  sucks 
up  the  foul  air  from  the  school-room  through  a  register ;  English  House 
of  Commons  uses  aspirating  chimneys ;  pure  air  drawn  down  one  chim- 
ney and  foul  air  drawn  up  another  (p.  72);  Montgolfier's  formula  for 
calculating  the  velocity  of  an  upward  current  in  a  chimney  (p.  74) ;  ob- 
jection to  carrying  down  the  foul-air  tubes  to  the  furnace  (p.  75) ;  neces- 
sity of  tall  chimneys  for  ventilating ;  efficiency  of  jets  of  steam  in  mov- 
ing air  (p.  76) ;  "  absolute  temperature  "  ;  the  distance  above  "  absolute 
zero  "  which  is  — 459'4°  Fahr. ;  best  to  combine  ventilating-flue  with  the 
smoke-chimney. 

CHAPTER  XII.  Movement  of  the  Air  by  Mechanical  Means. — Vacuum 
movement ;  place  in  the  foul-air  duct  an  extracting  fan  or  blower  (p.  79) ; 
or  let  the  blower  force  the  fresh  air  into  the  room,  a  better  method  be- 
cause it  fills  the  room  with  pure  air,  whereas  the  exhaust  fan  draws  out 
the  air  from  the  room,  but  does  not  regulate  the  quality  of  the  inflowing 
air ;  hence  impure  air  may  come  in  through  windows  and  doors  as  well  as 
fresh  air ;  the  "  plenum  movement "  forces  the  fresh  air  into  the  room, 
the  propeller  being  placed  in  the  inlet  duct ;  the  air  forced  into  the  room 
— perflation,  blowing  through  —  can  be  regulated  perfectly  in  all  cli- 
mates (p.  80) ;  the  plenum  movement  by  far  the  best  method  of  ven- 
tilating. 

CHAPTER  XIII.  Air-PropeUers. — Revolving  fans  used  for  the  most 
part ;  Dr.  Arnott's  ventilating  propeller  (p.  83) ;  Rittenger's  fan  (p.  84) ; 
Comb's  fan  (p.  87) ;  Blackman's  fan  as  modified  by  Hope  Brothers ;  pat- 
ent of  Hendry  and  others  (p.  88). 

CHAPTER  XIV.  Expense  of  the  Plenum  Movement. — Table  of  tem- 
peratures ;  number  of  months  that  fire  is  required  in  twenty-eight  cities  (p. 
91) ;  a  thermal  unit,  the  amount  of  heat  required  to  raise  the  temperature 
of  one  pound  of  water  1°  will  raise  48  cubic  feet  of  air  1"  (p.  92) ;  180,000 
feet  required  in  one  hour  in  a  school-room  of  60  pupils ;  hence,  to  raise 
that  temperature  35°,  the  average  amount  for  Chicago,  131,250  thermal 
units  per  hour  are  required ;  the  loss  of  heat  through  the  walls  exposed 
to  external  air,  for  4  walls,  7,937  thermal  units  per  hour  (p.  93) ;  loss 


ANALYSIS  OF  CONTENTS. 

through  6  windows,  3,572  thermal  units,  making  total  loss  per  hour,  for 
fresh  air  and  walls,  142,759  thermal  units,  requiring  18  pounds  of  coal  per 
hour ;  for  seven  months,  a  10-room  building  would  cost  $512,  if  coal  ia 
$5  per  ton  (p.  94) ;  this  about  the  actual  average  cost  of  fuel  in  buildings 
that  do  not  secure  ventilation,  but  use  the  same  air  30  to  60  minutes 
(p.  95)  ;  the  heat  is  ordinarily  wasted  by  windows,  doors,  too  small  heat- 
ing-surfaces, and  the  failure  to  introduce  warm  air  at  different  points 
in  the  room  (p.  96). 

CHAPTER  XV.  Cost  of  Ventilating  Apparatus. —  Cost  of  Aspirating 
Chimney  (p.  97) ;  to  secure  a  velocity  of  8  feet  per  second  for  the  air  in 
the  chimney  requires  21  pounds  of  coal  per  hour,  which  is  3  pounds 
more  than  is  required  to  heat  the  room,  making  the  aspirating  chimney 
expensive  unless  heated  by  the  smoke-stack  (p.  99);  diagram  of  aspi- 
rating chimney  heated  by  smoke-stack  (p.  100) ;  such  chimneys  usually 
made  too  small ;  should  furnish  at  least  6  square  feet  of  sectional  area 
for  each  room,  and  for  14  rooms  be  9  feet  square  (p.  101);  cost  of  the 
plenum  movement  (p.  1 02) ;  the  Rittenger  fan  requires  one  horse-power 
for  each  room,  and  5  to  8  pounds  of  coal  per  hour ;  the  Blackman  fan 
and  the  Hope  water-motor  fan  much  cheaper  (p.  102);  advantages  of 
plenum  movement — acts  in  all  weathers  and  establishes  current  of  fresh 
air  independent  of  windows  or  accidental  openings  (p.  103). 

CHAPTER  XVI.  Warming. — Temperature  of  the  room  should  be  70' 
for  school-rooms  (p.  104) ;  with  sluggish  circulation  of  blood,  a  person 
needs  a  higher  temperature;  transmission  of  heat  by  conduction,  con- 
vection, and  radiation  (p.  105) ;  heaters  should  be  large,  so  as  to  avoid 
overheating  of  surface ;  poisonous  gases  escape  from  a  red-hot  stove ; 
stoves,  steam-pipes,  and  stove-pipes  heat  by  conduction ;  an  open  fire  in 
a  grate  heats  by  radiation ;  radiant  heat  the  healthiest  (p.  106) ;  spec- 
trum analysis  (p.  107) ;  sanitary  effects  of  radiant  heat — it  warms  the 
body  without  heating  the  air  (p.  108) ;  but  warms  only  one  side  at  a  time 
(109) ;  convection  is  the  method  of  conveying  heat  by  the  movement  of 
currents  of  warm  air  (p.  110). 

CHAPTER  XVII.  Methods  of  Warming. — The  open  fireplace  in  the 
City  of  London  High-School  (p.  Ill) ;  Dr.  Arnott's  smokeless  grate  (112); 
description  of  it  (p.  113);  would  use  4  pounds  of  coal  per  hour  for  a 
school-room  30  x  30  x  14  feet ;  Boyd's  open  fireplace  provides  for  ad- 
mission of  cold  fresh  air  and  warming  it  (p.  1 14) ;  if  stoves  are  used, 
large  ones  should  be  selected,  so  as  to  avoid  overheating,  and  should  be 
lined  with  fire-brick — long  smoke-pipe,  extending  round  the  room,  so  as 
to  economize  the  heat  (p.  116);  stoves  the  cheapest  means  of  warming 


ANALYSIS  OF  CONTENTS.  xix 

known;  Dr.  Arnott's  self -regulating  stove  (p.  117);  smoke  consumed  by 
it ;  common  stove  with  a  drum  (p.  119) ;  improved  stoves  by  A.  M.  Hicks 
and  A.  Dishman,  of  Kentucky ;  Baltimore  Heater  (p.  120) ;  the  Ruttan 
system  discussed ;  Smead's  invention  for  mixing  hot  and  cold  fresh  air 
(p.  122) ;  escape  of  foul  air  at  the  bottom  of  the  room  in  the  Ruttan  sys- 
tem (p.  125) ;  necessity  of  strong  draft  to  secure  proper  ventilation  by 
this  system;  waste  of  heat  in  the  top  of  room  (p.  126);  necessity  of 
cleansing  foul-air  passages  ;  mistakes  or  neglect  of  builders. 

CHAPTER  XVIII.  Steam-Heating. — English  House  of  Commons  heated 
by  means  of  furnace- warmed  air,  on  a  modified  plan  of  Dr.  Reid  (p.  129) ; 
hot-air  chamber  beneath  the  floor,  foul-air  flues  at  the  top  of  the  room  ; 
amount  of  heat  conveyed  by  steam ;  experiment  to  prove  the  ratio  of 
latent  heat  in  water  to  sensible  heat  (p.  132) ;  upon  condensation,  all  the 
latent  heat  of  steam  becomes  sensible  heat ;  Mr.  Holly's  method  of  in- 
sulating steam-pipes ;  1,600  feet  of  3-inch  pipe  lost  by  radiation  only  2£ 
per  cent  (p.  134) ;  one  pound  of  coal  converts  9  pounds  of  water  into 
steam,  and  realizes  8,640  thermal  units ;  hence  16*66  pounds  of  coal 
necessary  to  supply  a  room  for  an  hour,  being  2  pounds  less  than  by 
furnace  heat  (p.  136);  direct  radiation  by  steam-coils  condemned,  unless 
ventilation  is  provided  ;  plan  of  room  with  proper  ventilation  (p.  138) ; 
Washington  school-buildings  heated  by  direct  radiation  and  without  ven- 
tilation (p.  139);  steam-pipes  extending  round  the  sides  of  the  room 
near  the  floor  (p.  140)  ;  heating  of  same  air  over  and  over ;  indirect  ra- 
diation by  steam-coils  placed  beneath  the  floor,  and  fresh  air  warmed  by 
passing  over  them  and  into  the  school-room ;  needs  a  good  aspirating 
chimney  or  a  ventilating  fan ;  steam  radiators  placed  under  windows,  in 
order  to  counteract  cold  currents,  or  near  the  inside  walls  of  the  room,  to 
save  loss  of  heat  (p.  143);  but  the  heat  ascends  to  the  top  of  the  room, 
and  is  not  distributed  properly. 

CHAPTEB  XIX.  Ideal  Plan  for  Warming  and  Ventilating. — The  feet 
should  be  kept  warmer  than  the  head  (p.  145) ;  plan  described  for  warm- 
ing and  distributing  fresh  air  through  the  floor  (p.  146) ;  'chimney  8  feet 
square,  with  foul-air  flues  opening  into  it  from  the  tops  of  rooms ;  fresh- 
air  shaft  bringing  down  the  air  from  the  top  of  the  building ;  registers 
along  the  aisles  by  the  side  of  the  desks  (p.  148);  method  of  cleansing 
the  registers  (p.  150) ;  method  of  creating  a  draft  in  warm  weather 
(p.  152) ;  three  pipes  to  regulate  the  amount  of  heat  supplied  (p.  153) ; 
double  joists  in  the  floor  necessary  for  this  plan ;  sufficient  ventilation 
without  resort  to  the  windows  ;  plan  of  16-room  school-house,  two  stories 
in  height  (p.  156) ;  chimneys  placed  between  the  rooms  ;  iron  ladders  inside 


XX  ANALYSIS  OF  CONTENTS. 

the  chimneys  (p.  157) ;  one  half  size  for  8-room  building ;  plan  for  a  6- 
or  12-room  building  (p.  158). 

APPENDIX. 

A.  Mr.  Glaisher's  observations  on  dry-  and  wet-bulb  thermometers ; 
his  factors  for  testing  the  moisture  of  the  air  (p.  161). 

B.  Simple  form  of  aspirating  chimney  (p.  164) ;  formulae  for  calcu- 
lating its  efficiency. 

C.  Formula?  for  constructing  Rittenger's  fan  (see  pp.  84-87). 

D.  Conducting  powers  of  materials  ;  copper  more  than  twice  the  con- 
ducting power  of  iron  and  zinc,  and  nearly  five  times  that  of  lead ;  19 
times  as  great  conducting  power  as  marble ;  100  times  that  of  brick ; 
300  times  that  of  oak. 

E.  Radiating  and  absorbing  power  of  bodies ;  silver  lowest  and  oil 
highest  (p.  168). 

F.  The  Blackman  fan  with  author's  improvements ;  drawings  show- 
ing formation  of  the  blades  (p.  170) ;  description  of  devices  to  prevent 
back-flow  of  air  (p.  171). 


PREFACE. 


THE  following  pages  are  not  intended  to  "  fill  a  long- 
felt  want."  The  greatest  necessities  are  often  not  felt 
as  wants.  If  an  individual  suffers  from  a  cause  which 
is  unknown  to  him,  he  feels  no  want,  necessarily,  to  re- 
move that  cause.  If  a  man  sickens  from  a  want  of  pure 
air,  without  knowing  the  cause  of  his  ailment,  he  never 
longs  for  a  more  salubrious  atmosphere  as  a  cure. 

I  am  fully  convinced  that  people  are  prematurely 
dying  by  thousands  simply  from  a  lack  of  correct  and 
positive  convictions  concerning  impure  air ;  for,  when 
the  true  nature  of  a  danger  is  fully  appreciated,  the 
requisite  means  to  avert  it  will  generally  be  found. 

Every  teacher,  or  other  person  who  works  in  a  viti- 
ated atmosphere,  has  doubtless  noticed  the  peculiarly  ex- 
hilarating effect  of  going  into  the  open  air  after  a  day's 
indoor  confinement.  My  own  experience  in  this  respect 
is  so  marked  that  I  seldom  step  from  a  crowded  room 
into  the  open  air  without  reflecting  on  the  nature  of  that 
invisible  cause  which  made  possible  a  change  so  sudden 
and  so  marked.  This  reflection  is  always  followed  by 
the  mental  query :  Can  not  this  great  difference  between 
the  qualities  of  outdoor  and  indoor  air  be  remedied? 


PREFACE. 

This  experience,  together  with  almost  daily  observation 
of  the  attempts  of  builders  to  ventilate  houses,  wherein 
the  simplest  physical  laws  are  commonly  ignored,  has 
led  to  the  writing  of  these  pages. 

The  work  is  confined  to  the  consideration  of  school- 
buildings  for  three  reasons  :  1.  I  am  better  acquainted 
with  the  needs  and  present  condition  of  school-houses 
than  of  any  other  class  of  buildings.  2.  These  build- 
ings, because  of  crowded  occupancy  during  successive 
days,  are  most  in  need  of  perfect  ventilation.  3. 
Knowledge  of  the  correct  principles  of  school-house 
ventilation  is  knowledge  equally  applicable  to  all  build- 
ings, as  the  same  principles  underly  all. 

Correct  theories  and  their  successful  application  to 
the  arts  of  life  can  not  be  conceived  and  executed  in 
a  day.  Our  knowledge  of  warming  and  ventilating 
is  a  growth  to  which  each  generation  has  probably  in 
some  measure  contributed.  Any  contribution,  there- 
fore, to  be  of  value,  must  be  made  in  the  full  light  of 
what  has  preceded  it.  In  preparation  for  the  present 
task,  therefore,  I  have  carefully  read  the  writings  of 
the  following  authors  who  have  contributed  to  this  sub- 
ject :  Parkes,  de  Chaumont,  Ritchie,  Hood,  Morin,  Ed- 
wards, Eassie,  Reid,  Arnott,  Tomlinson,  Billings,  Galton, 
Leeds,  Schumann,  Baldwin,  Draper,  and  Lincoln.  I 
also  procured  from  the  United  States  Patent  Office 
drawings  and  specifications  of  thirty  -different  ventilat- 
ing appliances  which  have  from  time  to  time  been  pa- 
tented. Whatever  the  Bureau  of  Education  has  fur- 
nished has  also  been  read.  The  best,  therefore,  that  has 
been  thought  or  done  on  this  subject  has  been  carefully 
studied,  and  whatever  is  valuable  has  become  assimi- 


PREFACE. 

lated  into  this  work,  in  so  far  as  it  informed,  invigorated, 
and  corrected  my  own  thought. 

The  chapter  on  window-ventilation  will,  I  think,  be 
useful  to  teachers.  While  windows  at  best  can  furnish 
only  partial  and  imperfect  ventilation,  it  is  only  by  their 
skillful  management  that  even  so  much  may  be  real- 
ized from  them. 

The  discussion  in  this  book  of  some  of  the  modern 
systems  of  warming  and  ventilating  is  made  from  an  in- 
dependent and  unbiased  study  of  their  merits,  and  with- 
out any  interest  in  advertising  either  their  excellences 
or  their  defects. 

The  ideal  plan  described  and  illustrated  in  the  last 
chapter  was  not  conceived  until  nearly  all  preceding  it 
had  been  written.  It  may  be  regarded,  therefore,  as  the 
result  of  a  long  and  exclusive  application  to  the  subject. 

For  valuable  suggestions,  I  wish  to  acknowledge  my 
obligations  to  Prof.  Wm.  Jones,  Professor  of  Chemistry 
in  the  Kansas  City  Medical  College,  for  reading  the 
manuscripts  on  the  chemical  examination  of  the  air ;  to 
Prof.  L.  Wiener,  of  the  Kansas  City  High  School,  for 
reading  the  mathematical  discussion  of  ventilating 
fans ;  and  to  Prof.  J.  M.  Greenwood,  Superintendent 
of  Kansas  City  Schools,  for  reading  the  same  and  other 
portions  of  the  manuscripts. 

G.  B.  MOBKISON. 

Kansas  City,  Mo. 


VENTILATION  AND  WARMING  OF 
SCHOOL-BUILDINGS. 


CHAPTER  I. 

NEEDED  INFORMATION. 

ADVICE  regarding  "fresh  air"  has  not  been  lacking 
in  amount.  Even  the  most  ignorant  have  some  indefinite 
notion  that  there  is  such  a  thing  as  "bad  air,"  and  that 
it  is  not  good  to  breathe  it.  Teachers  of  hygiene  pro- 
claim to  pupils  the  virtues  of  pure  air,  shut  up  in  school- 
houses  where  it  is  impossible  to  get  it.  Physicians 
advise  their  patients  to  take  fresh  air,  and  this  by  going 
out  of  doors,  thus  tacitly  realizing  that  it  can  not  be 
found  indoors.  Preachers  in  churches,  where  deadly 
gases  from  the  lungs  and  poisonous  organic  emanations 
from  the  skin  are  imprisoned  from  week  to  week,  em- 
phasize the  importance  of  properly  preserving  the  physi- 
cal body.  There  is  a  universal  recognition  that  it  is  bad 
to  breathe  impure  air  ;  there  is  an  ignorance  no  less  uni- 
versal of  the  conditions  of  how  to  avoid  it.  "When  the 
nature  and  composition  of  a  deadly  drug  are  known  and 
marked  "Poison, "it  is  properly  avoided.  In  the  next 
section  we  shall  see  that  much  of  the  air  we  breathe 
should  be  labeled  with  skull  and  cross-bones. 

Where  is  the  impure  air  ?    What  makes  it  impure? 
8 


12     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

What  are  the  nature  and  amount  of  the  impurities  ? 
These  are  important  questions  which,  among  the  edu- 
cated, are  tolerably  well  known.  But  when  these  im- 
purities exist  in  an  occupied  room,  how  are  they  to  be 
eliminated  and  replaced  by  pure  air  of  the  proper  tem- 
perature ?  These  are  questions  which  are  no  less  im- 
portant ;  but  they  are  questions  which  are  seldom  an- 
swered. How  to  know  where  impurities  exist ;  how  to 
expel  them  as  fast  as  formed,  and  supply  their  place 
with  the  pure,  life-giving  element,  is  a  problem  second 
in  usefulness  to  none  other.  Of  the  difficulty  of  the 
problem  we  have  ample  evidence  in  the  fact  that  it  has 
been  but  partially  solved,  and  in  general  practice  almost 
wholly  ignored.  True,  we  hear  men  talk  of  "  good 
ventilation"  and  "poor  ventilation,"  but  how  little  this 
generally  means  we  hope,  at  least  partially,  to  show  in 
the  pages  of  this  little  book. 

Of  the  lack  of  definite  information  on  this  all-impor- 
tant subject  we  have  abundant  evidence.  We  often  hear 
the  questions:  "What  is  the  best  way  to  ventilate  a 
school-room  ?  Whore  should  the  foul  air  escape  ?  Where 
should  the  pure  air  be  admitted?"  These  questions, 
among  the  first  to  be  met  in  ventilation,  show  that  even 
the  first  principles  of  matter  and  its  properties  are  not 
commonly  applied  to  the  gas  we  call  air. 

The  school-houses  throughout  the  United  States,  while 
they  are  elegant,  tasteful,  and  costly,  are  in  the  main  de- 
ficient in  their  sanitary  requirement  of  warming  and  ven- 
tilating. Whoever  may  be  disposed  to  doubt  the  truth 
of  this  statement  has  but  to  visit  the  nearest  school-house. 
Probably  in  nine  tenths  of  all  the  school-houses  in  this 
country  ventilation  has  been  ignored  altogether,  leaving 
that  important  function  to  be  performed  by  the  doors 
and  windows.  But  ventilation  should  be  independent  of 


NEEDED   INFORMATION.  13 

doors  and  windows,  which  are  primarily  intended  for 
other  purposes.  How  many  school -rooms  in  the  land 
could  maintain  a  school  with  doors  and  windows  made 
air-tight  ?  Probably  very  few,  and  in  the  majority  suffo- 
cation would  result  in  less  than  thirty  minutes  !  It  is  a 
sad  travesty  on  our  school  architecture  that  we  owe  our 
lives  to  the  mistakes  of  carpentry,  which  mistakes  arc 
usually  sufficiently  ample  to  supply,  in  a  crude,  unwhole- 
some, and  unsatisfactory  way,  the  deficiencies  of  direct 
ventilation. 

This  want  of  sufficient  and  definite  information  re- 
garding the  ventilation  of  school-houses  is  not  peculiar  to 
any  locality  ;  it  is  wide-spread  and  general.  Even  the 
District  of  Columbia,  which  is  under  the  direct  control 
of  the  Central  Government,  experiences  the  embarrass- 
ments which  this  all-important  but  vexed  problem  pre- 
sents. By  a  resolution  of  the  House  of  Representatives, 
dated  February  20,  1882,  a  commission  was  appointed  for 
the  purpose  of  investigating  the  public-school  buildings 
of  the  District  of  Columbia.  A  few  quotations  from  the 
report  of  this  committee  will  be  to  the  point :  "  The 
principal  defect,  from  a  sanitary  point  of  view,  in  all  these 
buildings  is  in  regard  to  the  fresh-air  supply,  which  is  en- 
tirely insufficient.  The  method  adopted  for  this  purpose 
is  to  admit  the  air  through  a  perforated  plate  placed  be- 
neath the  sills  of  four  windows  in  each  room.  Having 
passed  through  this  plate,  the  air  is  supposed  to  pass 
downward  through  a  narrow  slit  in  or  behind  the  wall, 
and  to  enter  the  room  at  a  level  with  the  floor  and  then 
pass  up  through  a  steam  radiator  which  is  placed  against 
the  window.  The  sum  of  the  clear  opening  in  the  exter- 
nal plate  of  each  window  is  from  twenty-two  to  twenty- 
five  square  inches,  so  that  the  area  of  clear  opening  for 
the  supply  of  pure  air  to  the  room  is  from  eighty-eight  to 


14     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

one  hundred  square  inches,  giving  an  average  of  about 
two  thirds  of  one  square  foot.  When  it  is  remembered 
that  this  is  intended  to  supply  fresh  air  for  sixty  children, 
each  of  whom  should  have  as  a  minimum  thirty  cubic 
feet  of  air -per  minute,  it  will  be  seen  that  it  is  simply  im- 
possible to  obtain  such  a  supply  through  the  openings 
provided,  which  in  fact  will  hardly  furnish  five  cubic  feet 
per  minute  per  pupil. " 

This  report  has  not  been  quoted  from  to  show  the  best 
that  has  been  done  in  school-house  ventilation,  but  rather 
what  may  be  considered  a  fair  representation  of  the  aver- 
age state  of  affairs  throughout  the  country. 

Something  toward  a  rational  system  of  warming  and 
ventilating  is  said  to  have  been  accomplished  at  the  Bos- 
ton High  School ;  also  at  Denver,  in  this  country ;  but 
more  especially  at  the  City  of  London  High  School,  and 
the  High  School  of  Vienna,  in  Europe. 

When  first  contemplating  the  preparation  of  this  vol- 
ume, I  thought  to  write  to  several  superintendents,  in 
cities  having  a  reputation  for  good  school-houses,  asking 
them  to  furnish  me  with  descriptions  of  their  system  of 
heating  and  ventilating,  that  I  might  use  them  as  a  feat- 
ure of  my  work,  incorporating  them  as  models  of  the  best 
modern  types  of  school-house  architecture.  Some  an- 
swered by  sending  a  pamphlet  in  which  ventilation  is  bare- 
ly referred  to ;  others  by  letter ;  but  the  average  signifi- 
cance of  them  all  may  be  given  in  the  exact  words  of 
one  of  them  :  "  Our  high  school  is  a  showy  building  on 
the  outside,  but  it  is  not  well  warmed  and  ventilated." 

Few  things  are  more  needed  than  a  systematic  dissemi- 
nation of  the  best  that  is  known  of  proper  methods  of  ven- 
tilation, as  well  as  stimuli  to  investigate  the  underlying 
principles.  A  subject  so  vital  to  the  health  and  safety  of 
the  growing  generation  should  be  investigated  by  every 


NEEDED   INFORMATION.  15 

teacher  of  physics,  and  the  known  laws  of  fluid  pressure 
and  motion  be  directly  applied  and  taught.  It  should  be 
a  theme  for  the  educated  physician,  whose  duty  it  is  not 
only  to  cure  disease  but  to  prevent  it.  It  should  be  the 
duty  of  every  school-house  architect  not  only  to  make  the 
best  practical  use  of  the  best  that  is  known  on  the  sub- 
ject, but  to  furnish  annual  reports  of  the  conditions  of 
the  school-buildings,  a  description  of  each  building,  the 
cost,  method  of  warming  and  ventilating,  the  air-space 
for  each  pupil,  the  percentage  of  heat  which  is  utilized 
in  the  consumption  of  fuel,  etc.  The  people's  right  to 
information  on  any  subject  should  be  measured  by  the 
value  and  indispensableness  of  the  information ;  and 
surely  nothing  is  of  more  universal  importance  than  the 
air  we  breathe,  affecting  as  it  does  our  health,  life,  and 
future  condition. 

The  .importance  of  this  kind  of  information  has  not 
been  wholly  ignored.  The  Denver  report  of  1883  con- 
tains a  chapter  on  school  architecture  in  which  the  stu- 
dious labors  of  the  architect,  Mr.  Kobert  S.  Eoeschlaub, 
are  laid  down  for  the  consideration  and  enlightenment  of 
the  public.  Many  valuable  hints  on  the  general  subject 
of  warming  and  ventilating  have  been  given  by  different 
writers  on  hygiene,  among  whom  may  be  mentioned  Pro- 
fessors Parkes  and  Draper.  From  a  purely  scientific  stand- 
point probably  the  most  has  been  done  by  Dr.  de  Chau- 
mont.  The  governments  of  France  and  England  have 
contributed  much  knowledge  on  the  subject  by  health 
commissions  appointed  to  investigate  the  sanitary  condi- 
tions of  barracks  occupied  by  soldiers ;  the  reports  of 
General  Moran  being  especially  valuable.  But  it  is  to 
Dr.  Neil  Arnott,  the  famous  Scotch  educator  and  physi- 
cian, that  humanity  owes  most  for  practical  knowledge 
on  warming  and  ventilating.  Deeply  versed  in  physics, 


16     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

being  the  author  of  a  valuable  text-book  on  that  sub- 
ject, he  understood  the  principles  and  laws  under- 
lying the  subject.  A  physician,  being  one  of  the  most 
eminent  in  the  realm,  he  well  understood  the  vitiating 
effects  of  impure  air.  A  practical  inventor,  he  put  his 
theories  in  practice  by  inventing  many  heating  and  venti- 
lating appliances,  among  which  may  be  mentioned  the 
Arnott  stove,  the  smokeless  grate,  and  an  automatic 
valve  for  admitting  fresh  air  to  fire-places.  A  philan- 
thropist, he  gave  his  thoughts  and  inventions  to  the 
world  free  of  charge,  -refraining  always  from  securing 
patents  and  copyrights.  He  did  not  overlook  the  needs 
of  the  schools;  he  applied  his  principles  to  the  "Field 
Lane.  Bagged  School " — by  a  method  to  be  noticed  here- 
after— with  excellent  results. 

A  little  reflection  will  answer  why  a  teacher  should 
undertake  to  contribute  to  this  important  subject.  The 
heaviest  blows  in  any  cause  have  always  been  struck  in 
self-defense.  The  teacher  is  defending  himself  in  en- 
deavoring to  better  the  atmospheric  condition  of  the 
school-room  where  he  spends  the  most  of  his  active  life. 
Whatever  may  be  said  in  the  defense  of  children  who  are 
submitted  to  the  contaminating  influences  of  an  impure 
atmosphere,  the  same  may  be  urged  with  tenfold  em- 
phasis in  the  defense  of  teachers ;  for  while  the  pupil's 
school  life  lasts  only  a  few  years,  the  teacher's  term  is  a 
life-time.  While  it  is  the  duty  and  desire  of  all  good 
men  to  help  others,  the  sternest  e'fforts  are  always  made 
in  the  direction  of  self-preservation,  which,  if  successful, 
will  increase  the  capacity  to  help  others.  I  offer  no 
apology,  therefore,  for  contributing  to  a  subject  in  which 
all  humanity,  and  especially  all  teachers,  are  so  deeply 
interested. 


THE  EFFECTS  OF  BKEATEING  IMPURE  AIR.  17 

CHAPTEK  II. 

THE    EFFECTS  OF  BREATHING    IMPURE  AIR. 

NONE  except  he  who  has  given  special  study  to  the 
facts  begins  to  realize  the  injurious  effects  of  breath- 
ing impure  air.  Every  one  knows  that  a  disagreeable 
feeling  accompanies  the  breathing  of  impure  air ;  that  a 
feeling  of  stupor;  inactivity,  drowsiness,  and  sometimes 
nausea,  headache,  and  vertigo,  result  directly  from  the 
occupancy  of  ill-ventilated  rooms.  These  sensations  are 
temporary,  and  are  experienced  only  while  the  cause  is 
active,  and  usually  the  only  thought  is  to  temporarily 
relieve  the  inconvenience  by  a  recess  or  a  break  for  fresh 
air.  Seldom  do  persons  reflect  on  the  ulterior  effects  of 
these  violations  of  Nature's  laws,  and  when  the  outer 
air  is  reached,  and  long  draughts  of  the  pure  element 
relieve  the  depressed  sensations,  and  send  the  invigorat- 
ing oxygenated  life-blood  current  coursing  through  the 
system,  raising  the  spirits  and  clearing  the  brain,  their 
reflection  usually  end  with  relief,  and,  when  more  or  less 
resuscitated  and  rescued  from  the  fatal  stupor  (I  use  the 
phrase  advisedly),  the  unsuspecting  victims  crawl  back 
into  their  "Black  Holes,"  again  to  fill  the  system  with 
gaseous  poisons,  thinking  of  it  only  as  an  unpleasant 
duty,  the  immediate  endurance  of  which  will  bring  sub- 
sequent freedom  and  relief.  But  this  is  a  great  mistake ; 
the  temporary  suffering  consequent  on  the  act  of  breath- 
ing vitiated  air  is  but  a  small  part  of  the  objection  to 
be  urged  against  it.  The  principal  charge  against  the 
breathing  of  impure  air  is  that  it  sows  the  seeds  of  dis- 
ease and  death,  the  length  of  time  in  which  the  subject 
will  succumb  being  in  proportion  to  his  strength  and 
power  of  endurance. 


18     VENTILATING  AND  WARMING    OF  SCHOOL-BUILDINGS. 

No  subject  has  been  more  carefully  and  intelligently 
studied  than  the  direct  and  ultimate  effects  of  impure  air 
on  the  human  system,  and  on  no  subject  is  there  more 
unanimity  of  competent  opinion.  Besides  the  general 
debilitating  and  weakening  effects,  which  render  the  sys- 
tem susceptible  to  infectious  diseases,  breathing  impure 
air  is  believed  by  the  best  authorities  to  be  a  direct 
cause  of  phthisis  (consumption)  and  its  accompanying 
diseases — catarrh,  bronchitis,  pneumonia,  and  many  oth- 
ers. 

The  individual  effects  of  breathing  separately  the 
foreign  gases  usually  found  in  the  atmosphere  need  not 
be  considered  here,  but  it  is  their  combined  effect,  com- 
bining as  they  do  with  organic  emanations  from  the  skin 
and  lungs,  that  chiefly  concerns  us  in  considering  the 
effect  of  impure  air  made  so  by  respiration.  Carbon- 
ic dioxide,  C02,  is  commonly  considered  the  poisonous 
substance  in  the  atmosphere  ;  this  is  in  the  main  untrue, 
for  moderately  large  quantities,  when  pure  and  mixed 
with  air,  can  be  breathed  with  impunity.  C02,  by  its 
inability  to  support  life,  will  produce  asphyxia  by  shut- 
ting out  the  needed  oxygen,  but  it  can  not  be  regarded 
as  a  poison.  Substantially  the  same  conclusions  have 
been  reached  by  Demarquay,  Angus  Smith,  W.  Miiller, 
Eulenberg,  and  Hirt,  all  of  whom  have  made  close  in- 
vestigations. It  is  when  mixed  with  the  organic  emana- 
tions from  the  skin  and  lungs  that  the  poisonous  quality 
seems  to  be  present ;  and  Gavarret  and  Hammond  found 
that  the  organic  matter  when  taken  alone  is  "highly 
poisonous."  It  seems,  therefore,  that  the  principal  poi- 
soning agents  in  impure  air  are  organic.  Nevertheless, 
the  amount  of  C08  in  the  air  is  highly  important,  for  its 
presence  is  a  very  good  index  of  the  amount  of  the  organic 
impurities,  and  to  measure  the  percentage  of  C02  is  indi- 


THE   EFFECTS   OF   BREATHING  IMPURE  AIR.  19 

rectly  to  measure  the  degree  of  vitiation  of  the  air.  (See 
Examination  of  the  Air.) 

On  the  disease-producing  effects  of  air  rendered  im- 
pure by  respiration  we  have  a  host  of  authorities.  The 
following  statistics  are  from  the  English  sanitary  record, 
given  by  Ransom,  showing  the  comparative  death-rate 
from  pulmonary  diseases  in  different  localities  where  the 
relative  impurities  are  known  to  vary  in  about  the  same 
ratio  as  is  shown  in  the  death-rate.  For  all  England, 
1865-'76,  3-54 ;  for  Salford,  5 -12  ;  Manchester,  7 '7  ;  West- 
moreland, one  of  the  healthiest  counties,  2 '27;  North 
Wales,  2 '51.  It  is,  of  course,  not  to  be  forgotten  that  other 
causes,  such  as  intemperance,  insufficient  and  improper 
food,  sedentary  pursuits,  etc.,  also  conspire  in  these  unfa- 
vorable localities  to  produce  the  final  result.  "  But,"  as 
Dr.  Parkes  remarks,  "allowing  the  fullest  effect  to  all 
other  agencies,  there  is  no  doubt  that  the  breathing  of  the 
vitiated  atmosphere  of  respiration  has  a  most  injurious 
effect  on  the  health."  Consumption  is  commonly  attrib- 
uted to  sudden  and  undue  exposure  to  wet  and  cold,  want 
of  sufficient  food,  clothing,  etc.,  but  Baudelocque  says  that 
"  impure  air  is  the  great  cause  of  consumption,  and  that 
hereditary  predisposition,  un cleanliness,  want  of  clothing, 
bad  food,  cold  and  humid  air,  are  by  themselves  non- 
effective."  The  following  paragraph  from  Parkes's  "Hy- 
giene "  I  copy  for  the  weight  of  authority  in  the  eminent 
names  mentioned  therein  : 

" Carmichael,  in  his  work  on  'Scrofula'  (1810),  gives 
some  most  striking  instances  where  impure  air,  bad  diet, 
and  deficient  exercise  concurred  together  to  produce  a 
most  formidable  mortality  from  phthisis.  In  one  in- 
stance in  the  Dublin  House  of  Industry,  where  scrofula 
was  formerly  so  common  as  to  be  thought  contagious, 
there  were  in  one  ward,  sixty  feet  long  by  eighteen  feet 


20     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

wide,  thirty-eight  beds,  each  containing  four  children ; 
the  atmosphere  was  so  bad  that  in  the  morning  the  air  of 
the  ward  was  unendurable.  In  some  of  the  schools  exam- 
ined by  Carmichael  the  diet  was  excellent,  and  the  only 
causes  for  the  excessive  phthisis  were  the  foul  air  and  the 
want  of  exercise.  This  was  the  case  also  in  the  house  and 
school  examined  by  Neil  Arnott  in  1832.  Lepelletier 
also  records  some  good  evidence.  Prof.  Alison,  of  Edin- 
burgh, and  Sir  James  Clark,  in  his  invaluable  work,  lay 
great  stress  on  it.  Neil  Arnott,  Toynbee,  Guy,  and  others, 
brought  forward  some  striking  examples  before  the  Health 
of  Towns  Commission.  Dr.  Henry  MacCormac  has  in- 
sisted with  great  cogency  on  this  mode  of  origin  of  phthi- 
sis ;  and  Dr.  Greenhow  also  enumerates  this  cause  as  oc- 
cupying a  prominent  place." 

Gavin  Milroy,  in  his  pamphlet  on  the  "  Health  of  the 
Royal  Navy,"  expresses  his  belief  that  the  extraordinary 
mortality  from  consumption  on  some  of  the  ships  was  due 
mainly  to  improper  ventilation.  The  writer  on  the  sub- 
ject of  "Consumption"  in  "  Chambers' s  Encyclopaedia" 
says:  "Among  the  determining  causes  of  consumption 
in  large  populations  the  best  ascertained  are  those  con- 
nected with  overcrowding  and  bad  ventilation."  Lan- 
genbeck,  an  eminent  anatomist,  says  that  the  prime  cause 
of  consumption  is  breathing  impure  air. 

Impure  air  is  also  believed  by  the  best  authorities  to 
be  one  of  the  principal  causes  of  epidemics.  Dr.  Carpen- 
ter, than  whom  there  is  no  abler  authority,  says  :  "It  is 
impossible  for  any  one  who  carefully  examines  the  evi- 
dence to  hesitate  for  a  moment  in  the  conclusion  that  the 
fatality  of  epidemics  is  almost  invariably  in  precise  pro- 
portion to  the  degree  in  which  an  impure  atmosphere  has 
been  habitually  respired."  The  Board  of  Health  of  New 
York  conclude  that  forty  per  cent  of  all  deaths  are  caused 


TIIE   EFFECTS  OF   BREATHING   IMPrRE   AIR.  21 

by  breathing  impure  air.  In  view  of  such  alarming  facts, 
this  same  board  declares:  "Viewing  the  causes  of  pre- 
ventable diseases,  and  their  fatal  results,  we  unhesitatingly 
state  that  the  first  sanitary  want  in  New  York  and  Brook- 
lyn is  ventilation."  Direct  experiment  described  in  an- 
other place,  no  less  than  the  direct  evidence  of  the  senses, 
proves  that  the  air  in  our  school-rooms  is  impure  in  al- 
most all  cases,  and  in  a  majority  of  them  to  a  degree  far 
beyond  the  danger  line. 

In  view  of  these  facts,  and  the  results  as  proved  by 
the  authorities  above  cited,  why  is  it  regarded  by  the 
public  with  such  indifference  ?  When  a  school-house  is 
blown  down  by  a  hurricane,  killing  and  maiming  a  score 
of  children,  it  is  justly  regarded  as  a  great  calamity  ;  a 
vacation  is  given  to  quiet  the  excited  fears  of  parents  and 
children ;  investigating  committees  are  appointed  to  lo- 
cate the  responsibility,  and  the  faces  of  the  whole  pop- 
ulace are  blanched  with  apprehension.  Why  is  this? 
Why  does  the  intelligent  parent  send  his  child  to  a 
school-room  pcorly  ventilated  and  crowded  with  chil- 
dren, some  of  whom  are  breathing  into  a  stagnant  air 
the  germs  of  disease  and  death,  while  others,  from  un- 
washed bodies,  are  delivering  into  it  their  deadly  ema- 
nations, and  all  without  a  protest  on  the  part  of  those 
even  who  provide  proper  hygienic  conditions  at  home  ? 
It  is  because  the  effects  of  the  one  are  immediate,  occupy 
little  time,  the  number  killed  can  be  actually  counted, 
and  the  exact  magnitude  of  the  calamity  estimated  all  at 
once.  In  the  other  case  the  process  is  slower,  but  of  far 
greater  extent ;  the  actual  results  are  by  the  general  pub- 
lic less  definitely  known,  and  custom  and  attention  to 
other  matters  divert  the  attention,  and  the  deadly  de- 
struction of  the  innocents  by  impure  air  goes  on  silently, 
constantly,  and  powerfully.  While  noisy  demonstrations 


22     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

like  that  of  the  cyclone  attract  attention,  and  inspire  fear 
and  terror,  it  is  in  the  silent  forces  that  the  danger  lies. 
Nature's  most  destructive  forces,  as  well  as  her  strongest 
constructive  ones,  are  silent  in  their  operations  ;  but  when 
Science  detects  a  silent,  insidious  enemy  to  human  welfare, 
it  is  not  only  our  duty  to  assume  an  attitude  of  self-defense 
and  self-protection,  but  it  should  be  regarded  as  folly 
not  to  do  so.  Could  the  real  effects  of  breathing  impure 
air  be  fully  realized  by  the  public,  and  the  actual  amount 
that  is  really  breathed  be  definitely  known,  such  a  knowl- 
edge would  constitute  a  most  powerful  stimulus  toward 
solving  the  problem  of  ventilation,  as  well  as  create  a  dis- 
position to  provide  the  means  necessary  thereto. 

The  effects  of  breathing  impure  air  thus  far  consid- 
ered are  pathological,  but  it  has  its  pedagogical  and  eco- 
nomical aspects.  Every  observing  teacher  knows  the 
immediate  relation  between  the  vitiated  air  in  the  school- 
room and  the  work  he  wishes  the  pupils  to  perform. 
Much  of  the  disappointment  of  poor  lessons  and  the  tend- 
ency to  disorder  are  due  directly  to  this  cause.  The 
brain  unsupplied  with  a  proper  amount  of  pure  blood  re- 
fuses to  act,  and  the  will  is  powerless  to  arouse  the  flag- 
ging energies  ;  the  general  feeling  of  discomfort,  dissatis- 
faction, and  unrest  which  always  accompanies  a  bad  state 
of  the  blood  breeds  most  of  the  school-room  squabbles, 
antagonism,  misunderstanding,  and  dislike  which  are 
wont  to  occur  between  teacher  and  pupil.  The  pupil 
apparently  at  variance  with  his  teacher  is  really  at  war 
with  his  own  feelings,  caused  by  an  impure  and  stagnated 
condition  of  the  blood.  The  teacher  who  sometimes 
thinks  the  pupils  are  all  conspiring  against  him,  and  who, 
with  dizzy  and  clouded  brain,  says  the  wrong  thing  at 
the  wrong  time,  is  really  struggling  with  the  poison  which, 
on  account  of  his  long  seclusion  from  the  cheerful  air,  has 


TI1E   EFFECTS  OF  BREATHING   IMPURE   AIR.  23 

taken  possession  of  him.  Teachers  observe  how  much 
more  satisfactory  is  the  work  of  the  first  hour  of  the  day 
than  that  of  any  subsequent  hour  ;  this  is  not  because  of 
weariness  of  the  pupils.,  it  is  because  they  are  made  stupid 
and  obtuse,  and  the  teachers  made  uneasy  and  fretful,  by 
the  accumulating  poisons  from  skin  and  lungs. 

From  an  economical  standpoint  it  would,  of  course, 
be  impossible  to  estimate  the  financial  waste  of  breathing 
impure  air,  but  it  can  not  but  be  enormous.  In  a  com- 
fortable atmosphere  of  proper  temperature  and  purity 
as  much  mental  labor  can  be  accomplished  in  one  hour 
as  can  be  accomplished  in  six  in  an  atmosphere  rendered 
impure  by  respiration.  This  is,  of  course,  but  a  random 
estimate,  but  I  am  quite  sure  that  whatever  of  error  it 
contains  is  on  the  side  of  underestimating  the  deteriorat- 
ing influences  of  impure  air  rather  than  of  overestimating 
the  value  of  pure  air.  If,  then,  we  suppose  perfect  ven- 
tilation possible,  and  that  this  estimate  is  not  overdrawn, 
the  conclusion  follows  that  in  those  school-rooms  where 
ventilation  is  imperfect  and  the  air  impure  six  sevenths 
of  the  money  expended  to  educate  a  child  is  wasted. 
Doubtless  this  will  appear  to  some  as  an  exaggerated 
statement ;  but,  if  we  accept  the  premises  (and  this  will 
readily  be  done  by  all  who  have  tried  to  think  in  an  un- 
ventilatcd  room),  the  conclusion  is  inevitable.  This  con- 
clusion supposes  that  perfect  ventilation  costs  no  more 
than  imperfect  or  no  ventilation  ;  while  this  is  not  strictly 
true,  tho  difference  is  insignificant  when  compared  with 
the  loss  we  are  considering.  In  any  discussion  of  the 
feasibility  of  incurring  the  additional  expense  of  the  most 
perfect  ventilation,  this  loss  occasioned  by  the  want  of 
such  ventilation  must  not  be  ignored. 


24     VENTILATION  AND  WARMING  OF  SCUOOL-BUILDINGS. 

CHAPTER  III. 

THE   AIR. 

TJie  Composition  of  the  Air. — The  gaseous  envelope 
which  surrounds  the  earth,  and  which  we  call  air,  is  one 
of  the  conditions  of  animal  and  plant  existence.  It  is 
evident,  therefore,  that  a  definite  knowledge  of  its  com- 
position and  properties  is  all  important.  In  order  to  in- 
vestigate the  abnormal  conditions  which  often  prevail, 
with  a  view  to  correcting  them,  we  must  first  know  the 
normal  conditions. 

The  air  is  composed  mainly  of  two  gases,  oxygen  and 
nitrogen,  in  the  proportion  of  about  21  of  the  former  to 
79  of  the  latter.  The  following,  from  Parkes's  "  Hygiene," 
is  probably  as  exact  as  has  yet  been  ascertained  : 

Oxygen 209-6  per  1,000  volumes. 

Nitrogen 790-0   "       "  " 

Carbonic  dioxide  (C02) '4   "       "  " 

Watery  vapor Varies  with  the  temperature. 

Ammonia Trace. 

Organic  matter 

Ozone.   . 

Salts  of  sodium Variable. 

Other  mineral  substances. 

Pure  air  is  usually  considered  as  consisting  exclusively 
of  oxygen  and  nitrogen,  all  other  elements  existing  as 
impurities  in  it.  But  as  the  air  is  a  mixture  of  the 
constituents,  and  not  a  chemical  compound,  and  as  the 
proportion  of  these  elements  is  variable,  it  seems  more 
reasonable  to  regard  as  the  true  normal  air  that  propor- 
tion of  the  different  elements  which  best  conserves  the 
ordinary  uses  of  air  in  the  support  of  plant  and  animal 
life.  Without  the  C02,  small  though  it  be,  the  air  would 


THE  AIR.  25 

be  wanting  in  that  constituent  which  plants  most  need  ; 
and  a  certain  amount  of  watery  vapor  is  equally  indis- 
pensable for  the  use  of  animals.  It  seems,  therefore,  that 
C03  and  watery  vapor,  in  the  proportions  above  men- 
tioned,* are  really  as  truly  constituents  of  air  as  oxygen 
and  nitrogen. 

Impurities  in  the  Air. — There  are  many  substances,  in 
many  forms  and  from  various  sources,  constantly  passing 
into  the  air,  tending  to  make  it  impure  and  unfit  for 
respiration.  Of  these,  those  which  more  especially  con- 
cern us  in  consideration  of  the  condition  of  our  school- 
houses  are  vapors  and  gases  from  the  skin  and  lungs, 
principally  C02  and  vapor  of  water ;  solid  particles  of 
scaly  epithelium  from  the  skin,  fibers  of  cotton,  wool, 
etc.,  bits  of  hair,  wood,  coal,  chalk-dust,  and  many  other 
things  which  have  a  tendency  to  enter  the  blood  through 
the  delicate  air-cells  in  the  lungs,  if  gaseous,  and  to  lodge 
in  the  air-passages  or  be  drawn  into  the  lungs  if  solid, 
there  to  irritate  by  their  presence,  and  poison  the  system 
by  their  decay. 

But  Nature,  when  not  hampered  by  man,  has  provided 
a  compensation  for  this  poisoning  process  by  a  counter 
process  of  purification.  The  winds  scatter  the  impurities, 
diluting  them  with  large  quantities  of  air,  oxidizing  them 
into  simple  compounds,  and  rendering  them  harmless. 
The  tendency  which  gases  have  to  diffuse  causes  poison- 
ous substances  to  be  rapidly  diluted,  to  such  a  degree  as 
to  destroy  their  destructive  power.  It  is  evident,  then, 
that  wherever  the  contaminating  process  is  active  there 
also  should  the  purifying  process  be  active.  Wherever 
an  unusual  amount  of  unwholesome  matter  is  being 

*  The  exact  amount  of  watery  vapor  in  the  air  which  best  serves  the 
purposes  of  respiration  is  not  definitely  known,  but,  as  far  as  ascertained, 
it  is  considered  to  be  about  seventy  per  cent  of  saturation. 
2 


26     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

evolved,  there  especially  should  the  purifying  conditions 
be  present ;  air  in  such  places,  to  remain  pure,  must  be 
changed  in  rapid  succession,  in  order  that  dilution,  diffu- 
sion, and  oxidation  may  fulfill  their  legitimate  functions. 
In  a  school-room  the  contaminating  process  can  not  but 
be  rapid,  and  wherever  ample  provision  is  not  made  for 
rapidly  changing  the  air  of  the  room  a  dangerous  con- 
dition of  affairs  is  sure  to  exist. 

In  addition  to  the  inorganic  substance  suspended  in 
the  air  there  is  a  vast  number  of  organized  bodies.  While 
some  of  these  organisms  are  to  be  found  in  pure  air,  they 
are  vastly  more  numerous  in  impure  air,  and  more  espe- 
cially in  that  impure  air  made  so  by  animals.  Ammonia 
seems  to  be  the  great  supporter  of  the  countless  hosts,  so 
much  so  that  the  amount  of  this  gas  found  present  in  the 
air  at  any  time  and  place  is  thought  to  be  a  fair  indication 
of  the  relative  number  of  organisms  there  present.  More 
than  two  hundred  distinct  forms  of  microscopic  animals 
have  been  discovered  in  the  atmosphere*  (Ehrenburg). 
The  precise  effect  of  these  organisms  on  health  is  not 
known,  but  it  is  generally  believed  the  effect  is  detri- 
mental. Bacteria  of  many  forms,  and  spores  of  fungi, 
are  also  found  in  the  air,  and  all  these  organisms  are 
known  to  thrive  in  the  organic  impurities  found  in  the 
air.  Painstaking  investigations  as  to  the  disease-producing 
power  of  these  organisms  have  been  in  progress  within 
the  past  few  years  by  Drs.  Koch  and  Pasteur,  and  while 
it  is  generally  believed  that  these  organisms  and  certain 
diseases  are  related  as  cause  and  effect,  no  definite  germ 
theory  of  disease  has  yet  (1886)  been  accepted  by  the 
medical  profession.  The  facts  that  are  known,  how- 

*  The  presence  of  organic  matter  in  the  air  may  be  shown  by  the 
aeroscope,  or  by  forcing  air  through  strong  sulphuric  acid,  when,  if  pres- 
ent, the  organic  matter  will  turn  the  acid  dark. 


TEE   AIR.  27 

ever,  and  in  which  we  are  here  interested  are  :  That  a 
large  number  of  impurities  exist  in  the  air — that  these 
impurities  congregate  in  inclosed,  unventilated  spaces 
where  they  are  produced,  and  that  they  have  a  detriment- 
al influence  on  the  health. 

The  external  air  from  which  the  school-room  must  be 
supplied  has  impurities  peculiar  to  itself  and  to  the  lo- 
cality whence  obtained.  Dust  and  smoke  exist  in  the  air 
in  large  quantities,  as  well  as  the  products  of  decaying  or- 
ganic matter  from  the  surface  of  the  earth.  Equal  quan- 
tities of  these  impurities  are  not  found  in  all  parts  of  the 
air.  Dust  and  smoke,  owing  to  their  tendency  to  settle, 
will  be  found  in  larger  quantities  nearest  the  earth.  In 
a  series  of  analyses  on  street-dust,  at  different  elevations, 
Tichborne  found  that  the  amount  of  dust  was  not  only 
inversely  proportional  to  the  elevation,  but  that  the  per- 
centage of  organic  matter  that  it  contained  decreases  with 
the  elevation  ;  street-dust  near  the  ground  containing  45 '2 
per  cent  of  organic  matter,  and  that  at  the  top  of  a  pillar 
134  feet  high  only  29 '7  per  cent.  The  same  must  be  true 
as  to  the  relative  quantity  of  organic  impurities  at  different 
elevations.  Gases  rising  from  decaying  matter  on  the 
earth  must  rise  a  certain  distance  before  they  can  come 
into  contact  with  sufficient  pure  air  to  dilute  and  diffuse 
them.  The  reason  why  "ground-air"  is  unwholesome 
is  thus  seen  to  be  evident.  The  importance  of  these  facts 
will  appear  when  we  come  to  consider  the  source  of  the 
fresh- air  supply  in  ventilation. 

There  are  other  sources  of  impurities,  not  to  be  over- 
looked, always  existing  in  rooms  heated  by  stoves  or  by 
the  direct  radiation  of  steam-pipes.  The  most  serious  of 
these  is  found  in  the  use  of  stoves,  which  give  off,  when 
hot,  a  poisonous  gas.  The  blue  flame  sometimes  noticed 
in  stoves,  when  coal  is  first  put  in,  is  due  to  the  burning 


28      VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

of  carbonic  monoxide — CO — a  very  poisonous  gas.  Iron, 
when  moderately  hot,  is  not  pervious  to  this  gas,  which 
then  passes  harmlessly  up  the  chimney ;  but,  when 
strongly  heated,  iron  loses  the  power  of  retaining  it,  be- 
comes pervious,  and  allows  the  poisonous  gas  to  escape 
into  the  room. 

Another  source  of  impurity,  which  is  common  both 
to  stoves  and  to  steam-pipes,  where  the  latter  are  exposed, 
is  in  the  burning  and  charring  of  small  particles  of  or- 
ganic matter  which  settle  on  them.  This  burning  is 
known  to  have  a  very  injurious  effect  on  the  breathing 
qualities  of  air  in  a  room,  and  should  be  remembered 
when  considering  the  choice  of  the  method  of  heating. 

Humidity  of  the  Air. — The  quantity  of  watery  vapor 
found  in  the  air  varies  with  the  locality,  temperature, 
and  various  local  conditions,  and  is  important  from  a 
sanitary  point  of  view.  The  right  proportion  of  moist- 
ure in  the  air  constitutes  one  of  the  conditions  of  a 
healthy  climate.  In  the  heating  and  ventilating  of  build- 
ings, where  the  proper  proportion  of  watery  vapor  is 
found  not  to  be  present,  it  may  be  supplied  by  artificial 
means.  A  knowledge,  therefore,  of  the  proper  condi- 
tions of  humidity,  as  well  as  a  knowledge  of  the  means  of 
supplying  them  when  absent,  is  thus  seen  to  be  impor- 
tant. 

In  crowded  school-rooms  the  symptoms  of  fainting 
often  evinced  by  pupils  is  thought  to  be  partly  or  wholly 
due  to  an  insufficient  amount  of  moisture  in  the  air  of 
the  room.  Other  physiological  symptoms  of  an  atmos- 
phere too  dry  are  parched  lips  and  tongue,  a  dry,  fever- 
ish condition  of  the  skin,  and,  in  those  children  predis- 
posed to  lung  diseases,  a  hacking  cough,  resulting  from 
the  desiccating  effect  of  excessively  dry  air  on  the  lungs 
and  bronchial  tubes. 


THE   AIR.  29 

The  drying  power  of  air  depends  not  so  much  upon 
the  actual  quantity  of  moisture  already  in  the  air,  as 
upon  the  capacity  of  the  air,  under  certain  conditions,  to 
receive  more ;  these  conditions  being  mainly  the  varia- 
tions of  temperature.  If  the  air  of  a  room  containing  a 
certain  amount  of  moisture  be  raised  in  temperature  sev- 
eral degrees,  its  capacity  for  more  moisture  may  be  much 
increased,  while  the  actual  amount  already  present  may 
not  be  materially  diminished.  Hot  air  expands,  and  is 
thereby  rendered  thirsty,  greedily  extracting  water  from 
everything  moist  with  which  it  comes  in  contact.  Air  at 
any  temperature,  when  it  contains  as  much  vapor  of  water 
as  it  can  hold  without  depositing  it  in  the  form  of  dew, 
fog,  etc.,  is  said  to  be  saturated,  but  it  is  plain  that  air 
which  is  saturated  at  one  temperature  will  cease  to  be  so 
at  a  higher  temperature  unless  more  moisture  be  added. 
This  point  of  saturation  is  called  the  dew-point.  The 
dew-point — the  temperature  at  which  the  vapor  in  the 
air  condenses — is,  therefore,  variable,  and  always  depend- 
ent on  the  amount  of  vapor  of  water  in  the  air.  The 
dew-point  is  taken  as  the  standard  in  estimating  the  hu- 
midity of  the  air,  and  is  taken  as  100  per  cent. 

The  sanitary  condition  of  the  air,  as  influenced  by 
humidity,  has  not  received  the  attention  that  its  im- 
portance demands,  yet  enough  has  been  done  to  enable  us 
to  estimate  within  limits  fairly  narrow.  Dr.  do  Chau- 
mont,  in  some  experiments  in  various  rooms  containing 
air  of  standard  respiratory  purity,  found  that  the  average 
humidity  is  73  per  cent  of  saturation.  This,  it  must  be 
remembered,  was  taken  in  England,  where  the  climate  is 
much  more  moist  than  that  of  America.  Probably  an 
humidity  somewhat  less  would  answer  for  our  climate,  but 
in  any  case  a  given  standard  must  be  regarded  as  only 
provisional,  changing  with  the  temperature  of  the  room 


30     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

at  the  time  of  testing  ;  63°  Fahr.  was  the  temperature  used 
in  the  experiments  of  de  Chaumont. 

Some  observations  have  been  made  in  this  country  by 
D.  L.  Huntington  at  the  Barnes  Hospital,  Washington, 
and  by  Dr.  Cowles  at  the  Boston  City  Hospital.  The 
results  are  as  follows  :  "  First  week  in  December,  1877. 
Average  external  temperature  38^°  ;  average  temperature 
of  the  wards,  from  71°  to  76°  Fahr.  Average  relative 
humidity,  from  44  to  49  per  cent  of  saturation  ;  of  outer 
air,  74."  This,  it  will  be  noticed,  shows  a  much  lower 
per  cent  of  moisture  in  the  room  than  that  given  by  the 
English  standard,  yet  it  was  claimed  that  notwithstand- 
ing this  small  quantity  "a  peculiar  feeling  of  freshness 
and  purity  was  perceived  by  those  who  entered  the  room." 

This  "peculiar  feeling"  which  is  always  experienced 
in  passing  into  a  warm  room  in  winter  is,  I  think,  hard- 
ly a  trustworthy  teat  of  the  atmospheric  purity ;  and  it 
seems  further  unreasonable  to  suppose  that  the  best  sani- 
tary conditions  would  admit  so  great  a  difference  as  74 
and  44  per  cent  between  the  outer  and  inner  air.  This 
opinion  will  be  further  strengthened  if  we  accept  the 
statement  of  Dr.  Parkes,  that  "  warmth  and  great  hu- 
midity are  borne  on  the  whole  more  easily  than  cold  and 
great  humidity."  There  is  little  doubt  that  some  differ- 
ence exists  in  the  amount  of  atmospheric  moisture  re- 
quired by  different  individuals,  but  arrangement  should 
always  be  made  to  suit  the  average  needs  of  the  majority. 
From  what  I  have  been  able  to  learn  from  study  and  ob- 
servation, I  believe  that  70  to  75  per  cent  may  safely  be 
taken  as  a  provisional  standard  of  humidity  for  the  air 
of  school-rooms. 

In  rooms  where  the  air  is  too  dry,  it  may  be  moistened 
in  winter  by  placing  shallow  vessels  of  .water  on  stoves, 
on  heating  coils  of  steam  or  hot-water  pipes,  or  in  the 


EXAMINATION   OF   THE  AIR.  31 

hot-air  ducts.  In  summer,  moistening  by  artificial  means 
will  seldom  be  required,  but  when,  on  account  of  unusual 
dry  ness  of  season,  the  conditions  so  require,  it  may  be  done 
by  sprinkling  floors  (not  a  very  advisable  method),  or  by 
ejecting  cold  water  in  spray  through  a  series  of  small  holes. 
The  humidity  of  the  air  may  be  determined  directly 
by  means  of  an  hygrometer,  or  indirectly  by  means  of  wet 
and  dry  bulb  thermometers.  In  most  hygrometers  a  bright 
surface  is  cooled  till  dew  is  deposited  thereon,  and  the 
temperature  then  noted.  Owing  to  the  sensitiveness  of 
hair  to  changes  in  humidity,  it  is  sometimes  made  use  of 
as  an  hygrometer  ;  hair  shortens  in  dry  and  lengthens  in 
moist  air ;  and  if  a  hair  be  fastened  by  one  end  to  an  in- 
flexible support  and  the  other  end  attached  to  one  end 
of  a  needle  hung  on  a  pivot,  the  other  end  of  the  needle 
moving  over  a  graduated  scale,  it  will  form  a  tolerably 
accurate  measure  of  humidity.  The  method  used  by  me 
is  that  of  the  wet  and  dry  bulb  thermometer  with  Glai- 
sher's  factors.  (See  Appendix  A.) 


CHAPTER  IV. 

EXAMINATION  OF   THE    AIR. 

Microscopic. — The  microscopic  examination  of  bodies 
suspended  in  the  air  is  rapidly  growing  in  importance. 
While  the  work  may  still  be  regarded  as  in  its  infancy, 
much  has  been  done  by  Koch,  Pasteur,  and  others,  to- 
ward determining  the  effect  on  the  health  of  organic 
microscopic  bodies  in  the  air. 

It  is,  of  course,  not  to  be  expected  of  one  who  is 
merely  testing  the  respirability  of  the  air  in  a  school- 


32     VENTILATION  AND  WARMIN6  OF  SCHOOL-BUILDINGS. 

room  to  search  for  specific  disease-producing  germs  ;  but  as 
large  quantities  of  dust,  smoke,  etc.,  suspended  in  the  air, 
tend  to  make  it  irrespirable  in  proportion  to  the  amount 
of  these  impurities  existing  therein,  a  knowledge  of  the 
relative  quantity  of  suspended  matter,  as  well  as  the  nature 
of  it,  becomes  a  necessary  part  of  the  work  of  testing  the 
fitness  of  air  for  respiration.  A  fair  knowledge  of  the 
respirable  quality  can  be  obtained  without  microscopic 
tests  ;  but  as  these  observations  are  otherwise  interesting 
and  instructive,  I  here  describe  the  method  used  by  me, 
which  is  only  one  of  the  many  now  in  use  by  microscopists. 

Arrange  a  series  of  Woulfe's  bottles  containing  pure 
distilled  water,  connected  by  tubes,  and  pass  through  this 
the  air  to  be  examined.  The  air  in  passing  through  the 
water  leaves  its  suspended  particles  in  the  water,  a  drop 
of  which  can  be  examined  under  the  microscope.  If  the 
water  was  pure  distilled,  all  matter  found  in  it  in  the 
experiment  came  from  the  air.* 

As  a  means  of  passing  the  air  through  the  water,  an 
air-pump  or  aspirator  may  be  used.  I  use  an  air-pump 
which  is  so  constructed  as  to  admit  the  easy  attachment 
of  a  small  tube.  The  cubical  capacity  of  the  cylinder 
being  known,  the  amount  of  air  drawn  through  the  water 
may  be  found  by  multiplying  the  capacity  of  the  cylinder 
by  the  number  of  strokes.  Should  such  a  pump  not  be 
accessible,  an  aspirator  may  be  made  by  taking  a  tin  vessel 
of  known  capacity,  with  an  opening  at  the  top  to  receive 
the  tube,  and  a  tap  below  to  let  out  the  water.  Fill  this 
with  water,  attach  the  tube  and  open  the  tap ;  as  the 
water  runs  down,  the  vessel  will  be  filled  with  air  drawn 
through  the  water. 

*  It  is  not,  as  some  suppose,  a  'native  characteristic  of  water  to  con- 
tain "  live  things."  Pure  water  is  absolutely  devoid  of  everything  except 
its  two  constituent  elements,  oxygen  and  hydrogen. 


EXAMINATION   OF   THE  AIR.  33 

The  nature  of  the  organisms  in  the  air  can  be  further 
studied,  if  desired,  by  passing  the  air  through  a  cultivat- 
ing solution,  which  is  set  aside  and  the  germs  carefully 
studied  from  day  to  day  as  they  develop.  A  solution  of 
isinglass,  two  parts  in  400  parts  of  pure  distilled  water 
(Fodor),  makes  a  good  medium. 

Chemical. — A  complete  analysis  of  impure  air  compre- 
hends the  quantitative  and  qualitative  tests  for  carbonic 
dioxide,  C02,  free  ammonia,  NH3,  and  other  nitrogenous 
matter,  oxidizable  matters,  nitrous  and  nitric  acids,  and 
hydrogen  sulphide,  H2S  ;  but  for  ordinary  practical  pur- 
poses the  determination  of  the  C02  is  by  far  the  most 
important,  and  is  ordinarily  the  only  one  which  need  be 
made.  While  the  poisonous  qualities  of  the  air  are  not 
wholly  due  to  the  presence  of  the  C02per  se,  the  amount 
of  this  gas  found  to  be  present  is,  in  air  made  impure  by 
respiration,  generally  a  good  measure  for  other  impurities 
to  which  the  poisonous  quality  is  principally  due.  Owing 
to  this  fact,  a  careful  test  for  the  amount  of  C02  contained 
in  a  given  atmosphere  is  generally  the  only  one  which 
need  be  made  where  air  is  tested  merely  to  determine  its 
respiratory  purity. 

The  mere  presence  of  C02  in  the  air  may  be  tested  by 
exposing  baryta-water  in  a  shallow  9pen  dish  ;  if  C02  is 
present,  a  white  deposit  of  barium  carbonate  will  be  formed 
on  the  surface  of  the  liquid,  the  amount  and  rapidity  of 
the  formation  being  proportional  to  the  amount  of  C02  in 
the  air.  The  exact  proportion  of  C02  in  a  given  quantity 
of  air  may  be  determined  by  different  processes  ;  but  that 
of  Pettenkofer,  which  is  familiar  to  me  by  use,  is  probably 
as  good  as  any.  Briefly  it  is  as  follows  :  Take  a  glass  bot- 
tle of  about  one  gallon  capacity — 4£  litres  ;  fill  the  bottle 
with  water  in  the  place  where  the  air  is  to  be  tested. 
Pour  out  the  water,  allowing  it  to  drain.  This  expels  the 


34     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

air  formerly  in  the  bottle,  and  fills  it  with  the  air  of  the 
room.  Now  pour  into  the  bottle  60  c.  c.  (cubic  centime- 
tres) of  clear  lime-  or  baryta- water ;  close  the  mouth  air- 
tight, and  shake.  Allow  this  to  stand  eight  hours  if  lime- 
water,  or  one  hour  if  baryta-water.  The  C02  will  all  be 
absorbed  by  the  water,  the  causticity  of  which  will  be 
lessened  in  proportion  to  the  quantity  of  C02  in  the 
vessel ;  the  C02,  being  acid,  neutralizing  the  lime  by 
forming  a  neutral  carbonate.  If  now  the  causticity  of 
the  water  be  known  before  and  after  the  C02  has  been 
united  with  it,  the  difference  will  show  the  amount  of' 
lime  which  has  united  with  C02.  To  find  the  causticity 
of  lime,  prepare  an  oxalic-acid  solution.*  Take  30  c.  c.  of 
fresh  lime-water,  like  that  used  in  the  first  part  of  the 
experiment,  and  mix  with  it  just  enough  of  the  oxalic 
solution  to  exactly  neutralize  it.f  The  amount  of  the 
oxalic  solution  which  will  be  required  to  do  this  will  be 
somewhere  between  34  and  41  milligrammes,  the  amount 
varying  with  the  temperature.  Now  take  30  c.  c.  of  the 
solution  in  the  large  bottle,  after  the  expiration  of  the 
prescribed  time,  and  try  how  much  of  the  oxalic  solution 
it  takes  exactly  to  neutralize  it.  The  difference  between 
this  and  the  preceding  shows  the  number  of  milligrammes 
of  lime  which  were  united  with  the  C02  contained  in  the 
air  in  the  bottle.  Multiply  this  difference  by  04795,J 

*  This  solution  is  prepared  by  dissolving  2'25  grammes  of  crystallized 
oxalic  acid  in  one  litre  of  pure  distilled  water ;  1  c.  c.  neutralizes  1  milli- 
gramme of  lime. 

f  It  will  be  neutralized  when  it  does  not  change  the  color  of  turmeric 
paper  dipped  into  it. 

£The  molecular  weight  of  CaO  (lime)  is  56,  and  that  of  C03,  44,  the 
weight  of  C0a  being  therefore  -££  that  of  lime.  The  ratio  between  weight 
and  volume  at  32°  Fahr.  is  -506.  Then  £$  x  -506  x  2  =  '795,  the  factor 
used  above.  The  reason  for  multiplying  by  2  will  be  evident  by  remember- 
ing that  only  30  c.  c.  of  the  lime-water  was  used  out  of  the  60  c.  c.  put  in. 


EXAMINATION   OF   THE   AIR.  35 

which  gives  the  number  of  c.  c.  of  C02  contained  in  the 
air  examined.  Find  the  amount  of  air  in  the  bottle  by 
subtracting  the  volume  of  the  lime-water  put  in,  60  c.  c., 
from  the  total  capacity  of  the  bottle  expressed  in  litres. 
The  c.c.  of  C02  divided  by  the  volume  of  air  will  give  the 
number  of  c.  c.  of  C02  in  1,000  parts  of  air.  The  follow- 
ing general  formula  will  be  found  useful  in  solving  ex- 
fa— a')  0-795  _, 
amples  :  x  =  - ^-3 .  Reference:  z=c.  c.  of  C02per 

litre ;  a  =  first  alkalinity  of  lime-water ;  a'=  alkalinity 
after  exposure  to  air  in  the  jar  ;  c  —  capacity  of  the  jar  ; 
d  =  space  occupied  by  the  lime-water.  When  the  air  is 
several  degrees  either  below  or  above  the  freezing  point,  as 
will  generally  be  the  case,  a  correction  for  temperature  must 
be  made,  as  a  given  volume  of  air  when  expanded  by  heat 
is  less  dense,  and  when  contracted  by  cold  more  dense, 
than  normal.  "  Air  expands  or  contracts  '2  per  cent  for 
every  degree  it  deviates  from  the  standard "  ;  hence  -2 
per  cent  added  to  the  result  for  every  degree  above  32° 
Fahr.,  or  subtracted  for  every  degree  below  32°  Fahr., 
will  be  a  sufficient  correction  for  temperature.  At  ordina- 
ry elevations  a  correction  for  pressure  will  not  be  necessary. 
The  following  example,  selected  from  a  series  of  ex- 
periments made  by  me,  will  be  sufficient  to  illustrate  the 
process.  By  first  testing  the  alkalinity  of  the  lime-water 
«=38  ;  after  exposure  a'=30  ;  c=4,500  c.  c.,  d  —60  c.  c. 

fQQ       HC\\  fi'^CK 

rru  lOO'^QUI    V     t  V<J          _,      .,.,-.  f   /-Nyv  -,     r\r\r\  1 

Then  x  —  ^    .  ,. .    — — =1-432  c.c.  of  C02  per  1,000  vol- 
4,500—60 

umes  of  air.  Correcting  for  temperature,  which  was  in 
this  instance  80°,  or  48°  above  32°:  48  X  '002+lXl '432= 
1-569.  As  there  are  only  -4  c.  c.  C03  in  air  of  standard 
purity,  the  above  test  shows  a  bad  condition  of  air. 

Prof.  William  Jones  proposes  the  following  modifica- 
tion of  this  method,  which  will  give  the  sa.me  results, 
5 


36     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

lessening  somewhat  the  work  of  calculation  where  a  large 
number  of  tests  are  made.  If  we  take  the  molecular 
weights  of  C03  and  H2C204  -f~  2H20  (oxalic  acid),  which 
are  43*89,  and  125 "7  respectively,  we  see  that  one  part  by 

125 '7 
weight  of  C03  is  equal  to  ,  or  2 '8639  by  weight  of 

~Lo  oJ 

H2C204  +  2H20  ;  and  as  one  part  by  weight  of  C02  is 
equal  to  0*5086  part  by  volume,  then  each  2  -8639  parts  of 
oxalic  acid  are  equal  to  0*5086  part  by  volume  of  carbonic 
acid.  Therefore  0-5086  : 28,639  : :  1 :  56,309,  or  5-6309  parts 
by  weight  of  oxalic  acid  are  equal  to  1  volume  of  carbonic 
acid  ;  consequently,  if  we  dissolve  5  "63  grains  of  crystal- 
lized oxalic  acid  in  1  litre  of  distilled  water,  1  c.  c.  of  this 
solution  will  be  equal  to  1  c.  c.  of  C02,  thus  indicating  the 
volume  of  C02  present  in  a  given  amount  of  air  by  the 
difference  in  the  number  of  cubic  centimetres  of  oxalic  acid 
solution  required  to  neutralize  a  given  amount  of  lime-  or 
baryta-water  before  and  after  shaking  with  the  air,  with- 
out any  more  calculation  ;  except  that  if  we  use  only  one 
half  the  amount  of  lime-water  that  has  been  shaken  with 
the  air,  it  will  be  necessary  to  multiply  the  result  by  2. 

In  the  absence  of  the  means  for  chemical  tests,  the 
sense  of  smell  by  a  healthy  person  may  be  employed  with 
fair  results.  Dr.  de  Chaumont  states  that  -4132  parts  of 
C02  per  1,000  volumes  of  air  can  be  barely  perceived  by 
the  sense  of  smell  carefully  exercised.  When  0*6708  of  a 
part  is  present  the  organic  matter  becomes  disagreeable, 
and  when  0*9054  of  a  part  is  present  it  becomes  offensive 
and  oppressive.  After  this  limit  has  been  reached,  and 
the  air  becomes  loaded  with  still  more  impurities,  the 
sense  of  smell  becomes  unable  to  detect  shades  of  differ- 
ence. He  concludes,  from  a  long  series  of  such  experi- 
ments, that  "  0*2  per  1,000  in  round  numbers  is  the  maxi- 
mum of  respiratory  impurity  admissible  in  a  properly 


EXAMINATION   OF   THE  AIR. 


37 


ventilated  air-space."  *  It  must  be  remembered  that  after 
the  first  few  minutes  in  the  room  the  sense  of  smell  be- 
comes unreliable.  This  test  can  be  applied  only  by  per- 
sons of  keen  sense  and  close  and  discriminating  judg- 
ment, and  then  only  at  the  moment  of  first  entrance  into 
the  room  from  pure  external  air. 

EXPERIMENTAL  TESTS. 


No.  of  examination.  .  .  . 

Time  of  day  at  which 
air  was  taken  ...   .  . 

1 

2 

3 

4 

11  A.  M. 

50 
8,  all  open 
above  and 
below. 

50° 
80° 
68° 
Strong 
breeze. 

8063 
1-669 

•507 
Steam  — 
direct  ra- 
diation. 
One  outlet, 
10x16  in., 
into  a  shaft 
without 
heat. 

2  P.M. 

55 
6,  three  of 
them  being 
open  at  the 
bottom. 
75° 
76° 
72° 
Calm. 

3-387 
1-923 

•513 
No  fire. 

By  windows 
only. 

11  A.  If. 

45 
8,  three  of 
them  raised 
from  the 
bottom. 
60° 
88° 
76° 
Gentle 
breeze. 

2-155 
1-642 

•493 
Steam  — 
direct  ra- 
diation. 
One  outlet, 
10x16  in., 
into  a  shaft 
without 
heat. 

4  P.  M. 

51 
4,  on  oppo- 
site sides 
and  all 
open. 
70° 
70° 
68° 
Gentle 
breeze. 

1-055 
•6415 

•486 
No  fire. 

No.   of  pupils  in    the 
room  

No.   and    condition   of 
windows. 

External  temperature.  . 

(  Above 
Internal  temp.  ]  Be,ow 

Condition  of  the  wind. 

No.  of  parts  of  C0a  in 
1,000    parts   of    air 
taken  from  near  ceil- 
inf.  . 

No.  of  parts  of  COj  in 
1,000   parts    of    air 
taken  from  near  the 
floor  

No.  of  parts  of  C04  in 
1,000  parts  of  exter- 
nal air  taken  outside 
the  building  

Method  of  heating.  .  .  . 
Method  of  ventilating. 

*  Boscoc  found  in  a  school  of  sixty-seven  boys  8'1  parts  of  C0t  per 


38     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

The  accompanying  tabulated  record  shows  the  results 
of  a  few  tests  made  by  me  on  specimens  of  air  taken  from 
different  school-rooms. 

These  results  show  —  first,  that  all  the  rooms  from 
which  air  was  taken  contained  an  amount  of  C03  consid- 
erably above  the  limit  of  respiratory  impurity  (i.  e.,  *4  +  '2 
=  *6  parts  in  1,000  parts  of  air);  secondly,  that  the  amount 
of  C02  is  due  not  so  much  to  the  number  of  hours  the 
room  had  been  occupied  as  to  the  conditions  of  ventila- 
tion. In  Experiment  4,  where  the  purest  air  was  found, 
the  room  had  been  occupied  all  day,  but  on  this  particu- 
lar day  the  weather  was  fine,  with  a  breeze  from  the  west. 
The  windows  were  on  opposite  sides,  east  and  west,  so 
that  a  current  of  air  was  passing  directly  through  the 
room.  On  some  other  day,  when  the  windows  might  have 
to  be  closed  on  account  of  bad  weather,  and  the  wind 
happened  to  blow  in  some  other  direction,  this  room 
would  have  no  ventilating  advantages  over  the  others. 
Thirdly,  that  C02  was  in  every  case  found  in  the  largest 
quantities  at  the  top  of  the  room  ;  and,  fourthly,  that  the 
external  air  is  generally  pure,  so  far  as  C02  is  concerned. 


CHAPTEE  V. 

AMOUNT   OF  AIE  EEQUIKED. 

"WHEN  decided  by  examination  that  the  air  of  a  school- 
room is  unfit  for  respiration,  the  question  naturally  pre- 
sents itself,  How  may  this  air  be  renewed,  and  what  should 

1,000.    Weaver  found  in  a  girls'  school  in  Leicester,  England,  5'28  parts 
per  1,000.    Pettenkofer  found  in  an  occupied  room  7'23  parts  per  1,000. 


AMOUNT  OF  AIR  REQUIRED.  39 

be  the  rate  of  this  renewal  in  order  that  it  may  be  main- 
tained in  a  state  of  respirable  purity  ?  Let"tis  consider 
the  latter  question  first :  The  amount  of  C02  evolved  by 
one  person  in  one  hour  is — adult  males,  0*7  of  a  cubic  foot ; 
adult  females,  0'6 ;  children,  0'4.  If  we  take  0'2  C02 
per  1,000  volumes  of  air  as  the  extreme  admissible  limit 
of  vitiation  (and  this  is  as  much  as  is  safely  admissible), 
the  number  of  cubic  feet  of  fresh  air  which  will  be  viti- 
ated by  each  person  in  one  hour  may  be  expressed  by  the 

formula  v  =  -r,  where  v  =  the  required  amount  of  fresh 

air  per  hour ;  a  =  the  amount  of  C02  exhaled  by  each 
person,  and  b  =  the  limit  of  admissible  impurity.  In  the 
case  of  children,  where  the  amount  of  C08  exhaled  is  0*4, 

0-4 

we  have  by  substitution  -  -  =  2.    5  in  the  formula  is  ex- 
0'ifi 

pressed  per  thousand  volumes ;  therefore  v  represents  the 
number  of  thousands  of  cubic  feet  of  air. 

The  number  of  cubic  feet  of  air  vitiated  by  each  child 
in  one  hour  is  2,000.  In  high-schools,  where  pupils  are 
large,  it  would  be  more  nearly  correct  to  use  0*6  of  a 
cubic  foot  as  the  amount  of  C02  evolved  by  each  ;  and  in 
colleges  0'7  of  a  cubic  foot,  the  amount  given  off  by 
adults.  These  conditions,  then,  would  require,  respect- 
ively, for  small  children,  2,000  cubic  feet  per  head ;  for 
high-school  pupils,  3,000  cubic  feet ;  and  for  college  stu- 
dents, 3,500  cubic  feet.  In  a  school-room  of  ordinary 
size  there  are  28  X  34  X  14  =  13,328  cubic  feet  of  air. 
From  the  foregoing  it  was  seen  that  each  child  requires 
2,000  cubic  feet  of  pure  air  per  hour ;  sixty  children — 
about  the  average  school  number — will  therefore  require 
the  same  amount  in  one  minute.  It  is  plain,  then,  to  see 
that  the  air  in  the  average  school-room,  were  there  no 
means  for  ventilation,  would  become  vitiated  in  less  than 


40     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

seven  minutes  — 13,328  -*-2,000  =  6-6.6+  min.  It  ap- 
pears evident,  then,  that  in  order  to  meet  the  require- 
ments of  perfect  ventilation  the  air  in  the  room  must  be 
changed  every  seven  minutes,  and  the  total  amount  of 
fresh  air  which  must  be  passed  through  a  school-room  of 
ordinary  capacity  and  occupancy  is  2,000  X  60  =  120,000 
cubic  feet  per  hour. 

After  the  first  few  minutes — the  time  required  to  viti- 
ate the  amount  of  air  the  room  contains — the  size  of  the 
room  makes  no  difference  in  the  constant  amount  re- 
quired. It  is  the  number  and  size  of  the  occupants  which 
must  regulate  the  amount  necessary  for  ventilation.  The 
size  of  the  room,  and  the  number  of  cubic  feet  to  be  sup- 
plied each  pupil,  are  important  only  for  the  fact  that  a 
given  amount  of  air  can  be  passed  through  a  large  room 
without  producing  strong  currents  more  easily  than  the 
same  amount  through  a  small  room.  The  size  of  the 
room,  therefore,  and  the  number  of  cubic  feet  per  head, 
are  no  indications  of  the  respiratory  quality  of  the  air 
therein  contained. 

How  to  Estimate  the  Amount  of  Air  passing  through 
a  Room. — The  air  passing  through  a  room  may  be  esti- 
mated either  by  measuring  it  as  it  comes  in  or  as  it  passes 
out.  Before  making  these  measurements  they  should  be 
made  intelligible  by  an  understanding  of  a  few  funda- 
mental properties  of  fluids,  of  which  air  is  one. 

All  movement  in  the  air  is  caused  by  an  inequality  of 
pressure  in  different  localities  due  to  inequality  of  heat. 
Wind — air  in  motion — is  simply  the  movement  of  the  air 
of  one  locality  toward  another  locality  containing  air  of 
less  density.  As  heat  expands  the  air,  making  it  lighter, 
the  movement  of  the  air  will  always  be  in  the  direction 
of  the  warmer  temperature.  The  air,  being  matter,  has 
weight,  and  is  subject  to  the  same  laws  of  pressure  and 


AMOUNT  OF  AIR  REQUIRED.  41 

falling  as  other  matter.  If  the  atmosphere  were  of  uni- 
form density  from  top  to  bottom,  it  would  form  an  en- 
velope around  the  earth  about  five  miles  in  depth. 

The  velocity  which  a  body  acquires  in  falling  is  ex- 
pressed by  the  formula  v  =  v2gH.,  where  v  =  velocity, 
H  =  height  through  which  the  body  falls,  g  =  the  accel- 
eration due  to  gravity.  This  is  nearly  equal  to  eight 
times  the  square  root  of  the  height,  and  for  simplicity 
may  be  so  expressed  :  8^/H. 

The  particles  which  constitute  a  fluid,  as  water  or  air, 
have  no  friction  among  themselves,  and  exert  pressure  in 
all  directions.  Another  fundamental  law  following  from 
this  is  that  fluids  will  pass  through  an  orifice  below  the 
surface  with  the  same  velocity  that  a  body  would  acquire 
in  falling  a  distance  equal  to  that  between  the  surface 
and  the  orifice ;  and  that,  when  passing  through  an  orifice 
in  a  partition  separating  the  fluid  from  another  fluid  of 
different  height,  the  velocity  will  be  equal  to  that  of  a 
body  falling  a  distance  equal  to  the  difference  of  the 
depth  of  the  fluids  on  the  two  sides.  The  pressure  of  the 
air  on  any  surface  near  the  earth  is  about  fifteen  pounds 
to  the  square  inch,  and  is  the  weight  of  a  column  of  air 
five  miles  in  height.  Air,  then,  would  rush  into  a  vacuum 
with  a  velocity  which  a  body  would  acquire  in  falling  five 
miles.  It  would  rush  into  a  room  containing  air  of  a  less 
pressure,  which  may  be  considered  as  a  partial  vacuum, 
with  a  velocity  due  to  a  height  which  represents  the  dif- 
ference between  outside  and  inside  pressure.  Now,  a  di- 
rect relation  exists  in  any  substance  between  weight  and 
density,  and  as  a  volume  of  air  increases  regularly  with 
the  temperature,  lessening  its  density  and  weight  in  the 
same  ratio,  a  means  for  measuring  the  difference  of  press- 
ure by  comparing  the  temperature  of  the  air  on  either 
side  of  the  partition  is  thus  afforded ;  and  this,  together 


42     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

with  a  comparison  of  the  relative  height  of  the  entrance 
and  exit  orifices  in  a  room,  enables  us  to  calculate  the 
velocity  with  which  air  is  passing. 

Air  expands  -^^  of  its  volume  for  every  degree  Fahr- 
enheit. The  height  through  which  a  body  would  fall 
having  the  required  velocity  which  we  are  considering 

is  expressed  by  the  formula  H  =  -„    - ,  where  II  =  the 

491 

height  through  which  a  body  would  fall  to  acquire  the 
velocity  under  consideration ;  h  =  height  from  the  en- 
trance to  the  exit  orifice  ;  t  =  the  difference  in  tempera- 
ture between  inside  and  outside.  By  substituting  this 
value  of  H  in  the  general  formula  (v  =  8  /v/  H)  for  falling 

bodies,  we  have  v  =  8 1/    .„.    in  feet  per  second. 

491 

Example  :    Suppose  li  =  14  ft.,  t  =  20° ;  then  v  = 

/14  X  20 

8y  — j— —  =  6 '032  -f-  ft.,  the  velocity  of  the  air  per  sec- 
ond. An  allowance  of  from  one  sixth  to  one  half  of  the 
theoretical  velocity  must  always  be  made  for  friction,* 
according  to  circumstances  and  special  peculiarities  of  the 
openings  and  ducts  or  tubes  leading  thereto.  Having 
found  the  velocity,  the  amount  of  fresh  air  may  be  found 
by  multiplying  the  velocity  by  the  sum  of  the  areas  of 
the  openings  expressed  in  feet. 

These  calculations  are  equally  true  whether  the  open- 
ings are  windows  or  apertures  constructed  especially  for 
ventilation.  When  windows  are  used,  a  difficulty  arises 
in  making  the  computation,  due  to  the  difficulty  of  ascer- 
taining where  the  air  enters  and  where  it  leaves  the  room; 
windows  on  different  sides  of  the  room,  being  of  the  same 

*  For  discussion  of  particular  cases  and  practical  formulas  for  deter- 
mining velocity,  see  Appendix  "  B." 


AMOUNT  OF  AIR  REQUIRED.  43 

distance  from  the  floor,  and  their  openings  at  different 
times  varying  in  position  and  size  to  suit  the  freaks  of 
the  occupants,  are  inlets  or  outlets  according  to  the  cir- 
cumstances. The  same  window  may  be  inlet  and  outlet 
at  the  same  time,  producing  cross-currents  and  strong 
draughts,  the  disagreeable  nature  of  which  is  well  known 
to  all  victims  of  window-ventilation. 

The  simple  conditions  governing  the  possibilities  of 
this  method  of  measuring  the  amount  of  air  which  is 
passing  through  a  room  are,  that  the  air  in  the  room 
must  be  of  a  higher  temperature  than  that  outside  ;  the 
air  must  pass  in  from  below  and  pass  out  above.  In  sum- 
mer, when  the  outside  temperature  is  equal  to  or  higher 
than  that  inside,  this  method  is  not  available.  It  is  also 
unreliable  when  the  wind  is  blowing,  unless  the  openings 
are  properly  guarded  against  the  unequal  pressure  due  to 
this  cause.* 

The  Anemometer. — "When  the  wind  is  blowing,  or  any 
of  the  conditions  of  the  above  method  of  measuring  the 
velocity  of  the  air  are  otherwise  not  complied  with,  the 
anemometer  must  be  used.  Of  these  instruments  many 
kinds  are  now  in  use,  but  in  principle  they  are  all  essen- 
tially the  same.  They  consist  of  fans  revolving  on  an 
axis  (after  the  manner  of  a  wind-mill)  which  is  connected 
by  wheel-work  with  an  indicator  showing  the  velocity  of 
the  air  which  is  moving  the  fans. 

Insufficiency  of  ordinary  Air- Supply. — School-houses 
which  make  pretensions  to  ventilation  other  than  by 
means  of  doors  and  windows  commonly  have  a  single 
register  for  the  admission  of  fresh  air,  and  one  for  the 
exit  of  foul  air.  These  are  variously  situated — some- 
times at  the  top  of  the  room,  sometimes  at  the  bottom, 

*  Sec  "  Regulating  the  Drafts  of  Openings,"  page  66. 


44     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

and  at  other  times  midway  between  floor  and  ceiling. 
The  proper  position  for  these  ventilating  openings  will  be 
considered  in  another  place  ;  but,  supposing  them  to  be 
situated  properly,  we  are  ready  from  the  foregoing  to  con- 
sider the  efficiency  of  these  breathing-holes. 

These  registers  are  usually  about  16  X  18  inches,  and 
sometimes  much  smaller ;  this  gives  a  total  area  for  the 
entrance  of  pure  air  of  288  square  inches,  or  2  square  feet; 
multiplying  by  6,  the  number  expressing  the  velocity  in 
the  example  previously  given  (where  the  height  of  the 
room  is  14  feet,  the  difference  between  the  temperature 
of  air  outside  and  inside  20°),  we  have  12,  the  number  of 
cubic  feet  of  air  passing  into  the  room  per  second ;  mul- 
tiplying this  by  3,600,  we  have  43,200,  the  number  of 
cubic  feet  of  air  passing  into  the  room  per  hour.  We  saw 
above  that  each  pupil  requires  2,000  cubic  feet  per  hour 
in  order  that  the  degree  of  vitiation  may  not  exceed  the 
limit,  0*2  of  a  part  of  C02  per  1,000  parts  of  air  ;  and  that 
sixty  pupils  require  120,000  cubic  feet  of  pure  air  per 
hour.  It  thus  becomes  evident  that  this  amount  of  open- 
ing will  ordinarily  supply  only  about  one  third  of  the 
quantity  of  air  required.  Air  passed  through  an  opening 
of  this  size,  in  order  to  be  sufficient,  would  have  to  move 
at  the  rate  of  about  eighteen  feet  per  second,  or  about 
eight  and  a  half  miles  per  hour.  When  air  is  moving 
two  miles  per  hour,  it  becomes  perceptible  to  the  senses  as 
wind  ;  and  if  it  were  passing  into  a  room  at  the  rate  of 
eight  miles  an  hour  it  would  be  a  breeze  which  would  be 
dangerous  to  the  pupils  sitting  near  it,  especially  if  it  was 
not  warmed  before  passing  in.  This  velocity  of  air  would 
be  neither  tolerable  nor  possible,  unless  it  should  be  first 
warmed  and  then  forced  into  the  room  by  means  of  aspi- 
rating chimneys,  or  by  mechanical  means  described  in 
another  place. 


GENERAL  PRINCIPLES  OF  VENTILATION.  45 

TJie  Distribution  of  Air. — No  less  important  than  the 
adequate  quantity  of  air  to  be  supplied  to  a  room  is  its 
proper  distribution.  This  is  impossible  where  but  a  sin- 
gle opening  is  furnished  for  admission,  and  the  same  for 
exit.  Under  these  conditions  the  air  may  pass  through 
the  room  in  a  narrow  current,  without  being  utilized  by 
mixing  with  the  vitiated  air  of  the  room. 

In  considering  these  single  openings  of  the  ordinary 
size,  I  have  supposed  the  conditions  such  as  to  make  them 
count  for  their  greatest  possible  utility  ;  but  when  we 
remember  that  they  are  often  misplaced — that  the  differ- 
ence in  internal  and  external  temperature  is  often  not  so 
favorable  as  the  case  considered;  that  the  passages  through 
which  the  air  must  pass  before  reaching  the  room,  and  in 
making  its  final  escape  in  leaving  it,  do  by  friction  greatly 
lessen  the  amount  given  by  the  theoretical  estimate;  and 
that  these  passages  are  often  neglected  and  impure — we 
are  forced  to  the  conclusion  that  this  much  provision  for 
furnishing  pure  air  to  a  school-room  is  in  its  effects,  if  not 
absolutely  nil,  so  very  little  that  it  may  be  ignored.  The 
further  conclusion  is,  that  what  air  pupils  generally  get 
comes  in  through  windows  and  doors. 


CHAPTER  VI. 

GENERAL   PRINCIPLES  OF  VENTILATION. 

HAVING  learned  something  of  the  nature  and  require- 
ments of  the  air  we  breathe,  of  the  source  of  its  impuri- 
ties, the  amount  needed,  and  the  way  by  which  it  may  bo 
measured,  we  are  ready  to  consider  how  a  room  is  to  be 
supplied  with  air  of  the  requisite  quantity  and  quality, 


46     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

and  how  its  proper  temperature  may  be  maintained.  How 
to  remove  the  air  from  a  room  as  fast  as  it  becomes  viti- 
ated, and  to  supply  its  place  with  pure  air  of  the  proper 
temperature,  are  questions  in  engineering,  to  answer  which 
is  at  once  necessary  and  difficult. 

The  difficulties  which  attend  the  answering  of  these 
questions  are  in  part  theoretical  and  in  part  mechanical ; 
theoretical,  in  that  all  devices  and  means  to  accomplish 
the  ends  of  ventilation  must  rest  on  general  principles, 
and  conform  to  the  known  laws  of  matter  and  motion  ; 
mechanical,  in  that  the  successful  application  of  the  most 
obvious  general  principle  implies  good  workmanship. 

The  most  perfect  theory  of  ventilation,  based  on  cor- 
rect physical  principles,  might  be  totally  defeated  in  its 
ends  by  a  bungling  carpenter.  These  important  ques- 
tions, then,  can  be  met  and  answered  only  by  accurate 
and  skillful  workmanship,  based  on  correct  theory. 

A  secondary  difficulty  attending  all  efforts  to  engineer 
air  is  that  it  is  invisible.  Could  the  air  and  the  impuri- 
ties which  it  contains  be  seen,  we  should  at  every  turn 
receive  practical  hints  how  to  move  it,  as  well  as  constant 
admonition  that  it  is  to  our  best  interests  to  do  so  ;  but, 
instead  of  the  advantages  which  the  visibility  of  the  air 
would  afford,  we  have  to  rely  on  our  knowledge  of  its 
properties  and  laws,  and  on  our  reason  in  interpreting  ex- 
isting causes  and  their  attendant  effects. 

Warming  and  ventilating  are  antagonistic  processes — 
the  one  is  addition,  the  other  subtraction  ;  the  one  a  giv- 
ing, the  other  a  taking  away.  But,  as  the  two  processes 
are  inseparably  connected  and  mutually  interdependent, 
it  will  be  necessary,  partially  at  least,  to  treat  of  them 
together. 

Natural  and  Artificial  Ventilation. — So  many  differ- 
ent devices  of  warming  and  ventilating  have  been  em- 


GENERAL  PRINCIPLES   OF  VENTILATION.  47 

ployed,  some  of  which  make  use  of  mechanical  means 
to  move  the  air,  that  ventilation  is  usually  considered 
under  two  classes — natural  and  artificial  ventilation. 

In  natural  ventilation  the  openings  are  so  constructed 
and  arranged  as  to  make  the  natural  forces  in  the  rising 
of  warm  air,  and  in  the  falling  of  cold  air,  do  the  work  of 
changing  the  air  of  the  room. 

In  artificial  ventilation,  the  air  is  forced  into  the  room 
by  mechanical  power. 

This  classification,  while  convenient  enough,  is,  after 
all,  entirely  arbitrary.  All  ventilation  is  in  one  sense 
artificial,  and  in  another  sense  all  ventilation  is  natural. 
"Natural"  ventilation  is  artificial,  as  it  requires  art  in 
making  the  openings  of  the  proper  construction  and  po- 
sition ;  "artificial"  ventilation  is  natural  in  that  natural 
laws  must  be  utilized  and  directed. 

Illustration  of  the  General  Theory  of  Ventilation. — 
As  the  laws  of  motion  and  pressure  governing  fluids  are 
equally  applicable  to  air  and  to  water,  the  following  in- 
teresting experiment  illustrates  the  general  theory  ol 
ventilation : 

Take  a  large  glass  jar  and  fill  it  with  clear  water  to 
represent  the  external  atmosphere.  Fill  a  large  square 
bottle,  having  apertures  near  the  top  and  bottom,  with 
colored  water  to  represent  the  internal  air  of  the  room 
and  its  impurities  ;  see  that  it  is  of  the  same  temperature 
as  the  water  in  the  jar,  and  then  suspend  the  bottle  in 
the  water  in  the  jar.  On  carefully  opening  the  apertures 
it  will  be  noticed  that  a  mingling  of  the  clear  and  colored 
waters  takes  place  very  slowly.  This  is  due  to  diffusion, 
and  illustrates  what  takes  place  in  the  air  when  the  in- 
ternal and  external  temperatures  are  equal  and  the  at- 
mosphere quiet.  If  now  the  colored  water  be  heated  to  a 

temperature  several  degrees  above  that  of  the  clear  water, 
6 


48     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

it  will  be  seen  to  rise  and  pass  out  of  the  upper  apertures, 
the  outside  clear  water,  being  heavier,  flowing  in  at  the 
lower  aperture.  The  colored  water  soon  passes  out,  leav- 
ing the  bottle  filled  with  the  pure  water.  This  illustrates 
ventilation  in  winter,  when  the  air  of  the  room  is  warmer 
than  that  outside.  If  the  colored  water  in  the  bottle  be 
cooled  by  ice  or  a  freezing  mixture,  and  the  outside  water 
be  warmed,  the  current  will  be  reversed ;  the  heavier, 
cool  colored  water  will  flow  out  at  the  lower  aperture, 
and  the  outside  clear  water  will  flow  in  through  the  upper 
one  to  fill  the  space  thus  left.  This  illustrates  the  action 
of  the  air  in  summer,  when  the  air  of  the  room  is  cooler 
than  the  air  outside. 


CHAPTER  VII. 

NATUKAL  VENTILATION". 

Position  of  Ventilators. — The  question  is  often  asked, 
Where  should  ventilators  be  placed  ?  Some  say  at  the 
top  of  the  room,  others  say  at  the  bottom ;  the  experi- 
ment described  in  the  foregoing  chapter  answers  this 
question.  When  only  the  conditions  of  ordinary  natural 
ventilation  are  present,  there  can  be  but  one  answer — 
ventilators  should  be  at  the  top  of  the  room.  The  air  in 
the  room,  when  warmer  than  the  outside  air,  must  come 
in  at  the  bottom  and  go  out  at  the  top  ;  and,  when  cooler 
than  the  outside  air,  must  com'e  in  at  the  top  and  pass 
out  at  the  bottom. 

This  movement  may  be  reversed,  but  it  must  be  done 
by  means  other  than  that  afforded  by  natural  ventilation; 
and,  even  in  the  plenum  movement  described  in  another 


NATURAL  VENTILATION.  49 

place,  it  is  always  the  part  of  economy  to  work  with  Na- 
ture, and  not  against  her. 

Ventilators  are  often  placed  near  the  floor  because  of 
the  erroneous  idea  that  the  foul  air  is  below.  The  fact 
that  C08  is  a  little  heavier  than  air  has  led  to  the  hasty 
conclusion  that  it  at  once  settles,  and  is  to  be  found  near 
the  floor.  The  facts  are  that  C03  forms  a  very  small  per- 
centage of  each  expired  breath,  and  its  temperature,  as  well 
as  that  of  the  air  from  the  lungs  with  which  it  is  mixed,  is 
when  leaving  the  mouth  much  higher  than  that  of  the  sur- 
rounding air  ;  it  is  therefore  lighter,  and  at  once  rises  ;  and 
the  tendency  it  has  toward  rapid  diffusion  prevents  its  sink- 
ing even  after  it  has  become  as  cool  as  the  air  of  the  room. 

The  tendency  which  gases  of  great  differences  of  den- 
sity have  to  diffuse,  even  against  the  force  of  gravity,  may 
be  illustrated  by  taking  two  bottles,  filled,  one  with  hy- 
drogen, the  lightest  gas  known,  and  the  other  with  the 
heavy  C02  gas  which  we  are  considering.  Connect  the 
bottles  by  a  glass  tube  passing  through  the  cork  stoppers 
of  each.  Leave  them  for  a  time  with  the  light  hydrogen 
above  and  the  heavy  C02  below,  and  in  a  short  time  they 
will  be  thoroughly  mixed,  the  heavy  gas  having  risen 
against  gravity  to  mix  with  the  hydrogen. 

In  certain  modern  systems  of  heating  and  ventilating, 
to  be  described  hereafter,  the  ventilating  ducts  are  placed 
near  the  floor.  This  is  thought  by  the  inventors  of  these 
systems  necessary  to  prevent  the  too  rapid  escape  of  the 
fresh  air  as  it  enters  the  room  and  immediately  rises  to 
the  top.  If  this  warm  air  were  properly  distributed  as  it 
entered,  it  would  be  sufficiently  vitiated  to  require  its 
removal  on  reaching  the  top  of  the  room  ;  but,  as  this  is 
seldom  the  case,  the  difficulty  is  met  by  placing  the  out- 
lets below,  allowing  the  upper  hot  air  to  press  the  cooler 
air  down  and  out. 

3 


50     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

As  a  justification  for  this  arrangement,  the  authors  of 
these  systems  have  tried  to  persuade  themselves  and  the 
public  that  the  foul  air  of  a  room  is  at  the  bottom,  and 
have  conducted  some  curious  experiments  to  prove  this  ; 
among  which  may  be  mentioned  those  of  Mr.  Leeds,  of 
Philadelphia. 

He  first  takes  a  large  glass  tube,  with  perforated  caps 
at  each  end,  as  represented  in  Fig.  1.  Smoke  is  blown 

FIG.  l. 


into  the  tuhe  through  the  rubber  tube  T.  It  will  first 
rise  to  the  top  of  the  tube,  but  on  cooling  it  soon  settles 
to  the  bottom  and  flows  out  at  A.  This  smoke  is  intended 
to  represent  the  carbonic-acid  gas,  C02,  from  the  lungs, 
which  it  is  claimed  by  this  experiment  will  fall  like  the 
smoke  at  a  temperature  of  from  60°  to  70°. 

This,  with  no  further  knowledge  of  the  nature  of 
smoke  and  C02,  would  readily  pass  for  a  legitimate  com- 
parison ;  but  a  moment's  reflection  reveals  a  fallacy. 
Smoke  is  solid  matter  in  a  fine  state  of  division  floating 
in  warm  rising  air.  When  the  air  cools  and  ceases  to" 
rise,  these  solid  particles  by  their  superior  specific  gravity 
fall.  But  C02  is  not  a  solid;  it  is  a  gas ;  and  gases  have 
the  property  of  rapid  diffusion.  The  relatively  small 
quantity  of  C03  at  any  one  time  rising  with  the  heated 
air  will  have  more  than  time  thoroughly  to  diffuse  in  the 
air  before  the  latter  cools  sufficiently  to  allow  the  settling 
of  a  similarly  suspended  solid. 

Another  alleged  proof,  by  the  same  author,  consists 


INLETS.  51 

of  admitting  some  C02  in  an  undiluted  state  into  an  in- 
closed space  in  which  tapers  are  burning  at  different 
heights.  The  C03  being  heavier  than  air,  when  thus 
poured  in,  of  course  sinks  to  the  bottom,  and  extinguishes 
the  lower  lights  first,  which  is  given  as  sufficient  proof 
that  foul  air  is  found  at  the  bottom  of  the  room.  Here 
the  quantity  of  C02  used,  and  the  time  given  for  its  dif- 
fusion, are  all  out  of  proportion  with  the  actual  con- 
ditions ever  existing  in  an  occupied  room. 

Experimental  demonstration  does  not  always  demon- 
strate. Nothing  may  be  more  misleading  in  its  teaching 
than  an  experiment  which  is  only  half  interpreted.  Should 
this  reasoning  be  thought  insufficient,  the  facts  may  be 
easily  ascertained  by  examining  the  air  for  C02.  (See 
Experimental  Tests,  page  37.) 


CHAPTER  VIII. 

INLETS. 

Position. — Inlets,  as  before  intimated,  should  be  placed 
near  the  floor.  It  is  sometimes  claimed  that  in  order  to 
avoid  cold  air  on  the  feet  the  inlets  should  be  placed  seven 
to  nine  feet  from  the  floor,  so  that  the  cold  air  on  entering 
may  sink  and  mingle  with  the  warmer  air  of  the  room  as 
it  descends.  Too  much  can  not  be  said  against  submitting 
the  occupants  of  a  room  to  cold  drafts  of  air ;  and  where 
the  air  is  allowed  to  enter  without  being  warmed,  or  with- 
out provision  being  made  for  its  warming  as  it  enters,  it 
'is  perhaps  less  objectionable  to  admit  the  air  from  above  ; 
but,  as  it  should  be  a  settled  principle  in  building  school- 
houses  that  the  air  should  never  enter  without  some  pro- 


52     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

vision  for  its  warming,  the  objection  to  its  admission 
from  below  disappears.  To  admit  it  from  anywhere  else 
is  practically  to  destroy  the  upward  direction  of  the  cur- 
rent, upon  which  the  regular  change  of  the  air  of  the  room 
mainly  depends. 

In  summer,  when  the  inside  air  is  sometimes  cooler 
than  the  outside,  the  ventilation  will  be  downward,  and 
the  inlet  and  outlet  openings  at  the  bottom  and  top  of 
the  rooms  respectively  will  change  functions,  the  air  com- 
ing in  at  the  top  and  going  out  at  the  bottom  ;  but  this 
is  not  often  the  case,  especially  in  school-houses  where 
school  is  not  in  session  during  the  hottest  weather. 

Total  Size  and  Distribution  of  Inlets. — Inlets  should, 
of  course,  be  of  sufficient  area  to  admit  the  requisite 
amount  of  air  without  requiring  so  high  a  velocity  as  to 
cause  drafts.  The  total  area  may  be  easily  approximated 

y 
by  the  formula  A  =  ,,  where  A  equals  the  sectional 

area  of  the  inlet ;  V  equals  the  volume  of  air  passing 
through  the  inlet  per  hour ;  v'  equals  the  velocity  of  air 
in  feet  per  second  through  the  inlet ;  3,600  equals  num- 
ber of  seconds  per  hour.  It  is  generally  more  convenient 
to  let  A  represent  the  number  of  cubic  feet  of  air  required 
per  hour  by  each  pupil,  then  the  amount  required  for 
any  number  of  pupils  can  easily  be  obtained.  The  value 
of  V  has  already  been  discussed.  (See  Appendix  "B.") 
Example  : 

What  will  be  the  total  sectional  area  of  inlets  required 
in  a  room  capable  of  accommodating  75  pupils  ?  If  each 
pupil  requires  3,000  cubic  feet  per  hour,  and  the  velocity 
with  which  the  air  can  be  admitted  is  found  to  be  7  feet 

per  second,  then  A  =  — -,     — =  =  "119  square  foot  =  17 '1 
o,  bOO  x  7 

square  inches  for  each  pupil.     By  referring  to  the  exam- 


INLETS.  53 

pie  in  Appendix  "B,"  it  will  be  seen  that  7*7  is  the  ve- 
locity attained  when  a  good  aspirating  chimney  is  used. 
It  often  happens  in  ordinary  conditions  of  natural  venti- 
lation that  the  velocity  is  not  more  than  5  feet  per  second. 

3,000 
Using  this  number  m  the  above  problem,  A  =     6QQv.r  = 

£  square  foot,  or  24  square  inches.  Counting  60  as  the 
number  of  pupils  to  be  supplied,  the  total  area  of  inlets 
will  be  60  X  24  =  1,440  square  inches.  This  is  equal  to 
one  inlet  37 '8  inches  square,  or  10  square  feet.  About 
the  same  area  is  required  for  outlets,  making  20  square 
feet  as  the  total  area  required  for  inlets  and  outlets  in  an 
ordinary  school-room. 

Distribution  of  Inlets. — The  air  should  never  be  ad- 
mitted through  a  single  inlet,  but  should  be  so  distributed 
around  the  room  that  free  diffusion  may  occur.  To  pass 
air  into  a  single  opening  of  a  large  room,  and  allow  it  to 
pass  directly  out  at  another  opening,  may  be  likened  to  a 
waiter  who  would  feed  a  company  by  carrying  a  quantity 
of  food  through  a  dining-room  without  stopping  to  pass 
it  around.  One  foot  square  is  large  enough  for  one 
opening.  In  the  example  given  above  we  have  then  ten 
openings,  which  should  be  equally  distributed  around  the 
room ;  the  same  number  of  outlets  would  not  be  re- 
quired, though  they  must  be  equal  in  area. 

Source  of  the  Air  supplying  Inlets. — It  is  an  im- 
portant matter,  though  often  overlooked,  that  the  air 
which  furnishes  the  supply  to  inlets  should  come  from 
a  pure  source.  It  is  generally  understood  that  the  sur- 
face condition  of  any  locality  determines  largely  the 
condition  of  the  air  which  comes  in  contact  with  that 
surface.  A  wind,  if  blowing  over  an  icy  region,  will  be 
cold  ;  if  across  a  dry  and  arid  region,  it  will  be  dry,  des- 
iccating, and  parching ;  if  over  a  swampy,  wet  locality, 


54:     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

where  large  quantities  of  organic  matter  are  in  a  state  of 
decay,  it  will  be  laden  with  sickening  vapors  and  mala- 
rial germs. 

In  full  knowledge  of  these  universally  recognized  facts, 
the  air  which  furnishes  the  inlets  is  often  drawn  from 
near  the  damp  ground,  and  sometimes  from  the  vicinity 
of  back  yards  and  alleys,  where  all  kinds  of  filth  and  ref- 
use pollute  this  "fresh  supply"  before  it  enters  the 
school-room. 

Unless  the  school-house  is  extremely  fortunate  in  its 
location-site,  and  at  some  distance  away  from  all  other 
buildings,  the  air  supply  should  be  drawn  at  some  dis- 
tance from  the  ground,  by  means  of  upright  shafts  or 
tubes  of  the  height  determined  by  the  circumstances  of 
each  case.  Fig.  2  illustrates  the  movement  of  the  air 
down  the  shaft,  through  the  room,  and  out  at  the  venti- 
lator. A,  downcast  tube,  with  conical-shaped  cap  in- 
verted ;  B,  entrance  shaft ;  C,  upcast  cowl,  with  conical- 
shaped  cap  erect ;  D,  outlets  in  the  ceiling ;  E,  registers 
admitting  air  into  the  room  ;  E,  room  ;  W,  windows. 

The  chief  objection  to  the  use  of  down  shafts  for  the 
purpose  of  getting  pure  air  is  to  be  found  in  the  retarda- 
tion due  to  the  friction.  This  may  be  entirely  overcome 
by  means  of  aspirating  chimneys,  but  even  when  these 
are  absent  the  friction  may  be  largely  compensated  for  by 
properly  arranging  the  shape  of  the  shafts  and  ventila- 
tors. Reference  to  Fig.  2  will  show  how  this  may  be  done: 
the  wind  striking  the  inclined  surface  of  the  inverted 
conical  cap  is  deflected  downward  into  the  shaft,  thus 
increasing  the  amount  of  air  entering  the  room.  In  the 
ventilator  C,  on  the  other  hand,  the  wind  striking  against 
the  oppositely  inclined  surface  of  the  erect  conical  cap,  as 
well  as  the  flange  C'  below,  is  deflected  upward,  causing 
an  upward  draft  in  the  ventilating  tube. 


INLETS. 


55 


"Lobster-backed"  cowls  are  sometimes  used  on  venti- 
lators to  increase  their  aspirating  power.     These  revolve 

FIG.  2. 


with  the  wind,  keeping  the  back  to  the  windward,  thus 
preventing  the  wind  from  blowing  down  the  tube ;  the 


56     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

liability,  however,  of  these  cowls  to  get  out  of  order  has 
led  to  their  disuse. 

All  shafts  and  tubes  leading  to  the  room  should  be  so 
constructed  as  to  reduce  friction  to  a  minimum,  and  ad- 
mit of  frequent  cleaning  ;  they  should  therefore  be  lined 
with  some  smooth,  hard  material,  and  be  made  accessible 
to  the  brush  of  the  janitor.  Neglect  in  this  particular  is 
often  a  considerable  source  of  vitiation.  Rough  brick  and 
mortar  shafts  and  ducts  collect  large  quantities  of  dirt 
and  organic  matter,  which  by  its  decay  forms  a  source  of 
pollution,  and,  being  by  their  construction  inaccessible, 
their  vitiating  action  is  constant. 


CHAPTER  IX. 

REGULATING  THE  DRAFT  OF  OPENINGS — THE  WIND. 

WE  have  discussed  in  another  place  the  nature  and 
velocity  of  air  passing  through  inlets  and  outlets,  when 
caused  by  the  inequality  of  internal  and  external  temper- 
ature, and  the  difference  in  height  between  inlets  and 
outlets.  But  the  results  thus  obtained  will  nearly  always 
be  modified  by  the  action  of  the  wind,  which  is  usually 
blowing  in  some  degree,  and  which  must  be  in  some  man- 
ner compensated  for  by  properly  arranged  inlets. 

The  action  of  the  wind  is  to  increase  the  pressure  of 
the  air  on  the  windward  side  of  the  room,  and  by  the  aspi- 
rating power  which  a  moving  air-current  has  on  neigh- 
boring air  to  decrease  the  normal  pressure  on  the  leeward 
side.  The  extra  pressure  exerted  by  the  wind  may  be 
estimated  by  first  ascertaining  the  velocity  by  means  of  an 
anemometer  (q.  v.),  squaring  and  multiplying  by  *005. 


REGULATING  THE  DRAFT  OF  OPENINGS.  57 

This  is  expressed  by  the  empirical  formula  vsX  "005  =  P, 
where  v  =  velocity  of  the  wind,  P  =  pressure  iu  pounds 
per  square  foot,  and  '005  =  a  constant. 

When  an  anemometer  is  not  accessible,  a  tolerably 
correct  estimate  of  the  wind's  pressure  may  be  obtained 
by  Beaufort's  classification  of  winds  :  1,  faint  air;  2,  light 
air  ;  3,  light  breeze ;  4,  gentle  breeze  ;  5,  fresh  breeze  ;  6, 
gentle  gale;  7,  moderate  gale;  8,  brisk  gale;  9,  fresh  gale; 
10,  strong  gale;  11,  hard  gale;  12,  storm.  In  this  classi- 
fication the  force  of  the  wind  is  estimated  by  the  scale  0 
to  12,  which  represents  all  degrees  from  a  calm  to  a  hur- 
ricane. In  using  this,  any  estimate  divided  by  2,  and 
the  result  squared,  will  approximately  represent  the  wind's 
pressure  in  pounds.  Example:  Suppose  a  " gentle  breeze " 
is  blowing.  Referring  to  the  classification  above,  it  is 
seen  that  "gentle  breeze"  is  No.  4;  then  (f)2  =  4,  the 
number  of  pounds  pressure  on  one  square  foot  of  surface. 
Again:  If  a  "strong  gale  "is  blowing,  then  (^)2  =  25 
pounds. 

In  the  absence  of  an  anemometer,  the  velocities  of  the 
different  winds  above  enumerated  may  be  calculated  by 
finding  the  pressure  in  each  by  the  method  last  given, 
and  then  substitute  this  value  of  P  in  the  first  formula, 
from  which  then  find  the  value  of  v.  For  convenient 
reference  I  have  made  th»  calculations,  which  may  be 
considered  as  simply  a  popular  translation  into  the  com- 
mon language  of  terms  used  in  referring  to  wind  : 

1.  Faint  air,  7  miles  per  hour. 

2.  Light  air,          14     " 

3.  Light  breeze,     21      "  " 

4.  Gentle  breeze,   28     "  " 

5.  Fresh  breeze,     35     "  " 
G.  Gentle  gale,       42     "            " 
7.  Moderate  gale,  49     "            " 


58     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

8.  Brisk  gale,         56  miles  per  hour. 

9.  Fresh  gale,         63      "  " 

10.  Strong  gale,       70     "  " 

11.  Hard  gale,         78     "  " 

12.  Storm,  85     "  " 

If  action  of  the  wind  is  not  anticipated  and  provided 
for,  it  will  defeat  the  most  carefully  laid  plans  for  venti- 
lation ;  but,  if  properly  controlled,  it  may  by  its  perflat- 
ing,  aspirating,  and  motive  power  be  made  an  aid  instead 
of  being  a  hindrance.  By  its  perflating  power  it  may  be 
used  in  counteracting  friction  by  directing  the  current 
downward  through  entrance  shafts,  as  shown  in  Fig.  2  A. 
By  its  aspirating  power  it  may  increase  the  upward  draft 
of  a  ventilator  chimney  by  blowing  directly  across  the 
top,  or  by  being  directed  upward  by  means  of  a  deflecting 
surface  (Fig.  2  C). 

When  inlets  are  not  preceded  by  down-shafts,  but  only 
by  short  tubes  or  ducts  coming  directly  from  the  outer 
air,  they  should  be  guarded  by  means  of  guards  or  valves, 
to  prevent  strong  gusts  of  wind  from  entering  the  room, 
which  might  otherwise  occur.  The  best  possible  arrange- 
ment for  this  purpose  would  be  a  modified  form  of  Dr. 
Arnott's  current-regulating  air-valve,  which  he  invented 
for  regulating  the  draft  of  closed  stoves.  A  sectional 


FIG.  3.  _ 


A 


B  I 

diagram  of  this  ingenious  device  is  here  represented  (Fig. 
3).     The  bounding  lines  H  E  I  K  represent  the  outside 


REGULATING   THE  DRAFT   OF  OPENINGS.  59 

walls  of  the  tube  to  be  fitted  into  the  inlet  duct.  The 
arrows  show  the  direction  of  the  air-current ;  A I  is  the 
opening  of  the  inner  extremity  of  the  box,  and  D  H  the 
opening  to  the  outer  extremity.  G  E  represents  the  edge 
of  a  lever-frame  balanced  across  the  partition  C  B.  F  G 
is  a  door  attached  to  the  lower  extremity  of  the  lever- 
frame  EG.  W  is  a  sliding  weight  on  the  rod  extending 
from  F.  The  half  of  the  lever-frame  shown  by  the  broken 
line  C  E  is  covered  by  a  wire  screen,  through  which  the 
air-current  flows  in  its  passage  into  the  room.  If  the 
current  is  strong,  it  is  resisted  somewhat  by  the  friction 
against  the  wires.  This  resistance  causes  the  screen  end  of 

o 

the  frame  to  be  depressed,  and  the  opposite  end,  carrying 
the  door  F,  to  be  elevated — thus  partly  closing  aperture 
H  D.  The  size  of  the  opening  will  thus  always  be  in- 
versely proportional  to  the  strength  of  the  wind.  When 
out  of  proper  balance,  it  may  be  corrected  by  moving  the 
weight  W.  v  This  device  is  remarkable  for  its  ingenious 
simplicity,  and  it  is  also  remarkable  that  it  has  never 
been  utilized  as  a  current-regulator  in  ventilation. 

Various  devices  have  been  contrived  at  the  inner  ter- 
minus of  inlets  for  preventing  a  perceptible  draft  on  the 
windward  side  of  buildings,  among  which  may  be  men- 
tioned the  Shirringham  valve,  which  gives  the  wind  a  de- 
flection upward  as  it  enters  the  room.  Other  forms  have 
been  made  by  Messrs.  Bayle,  Weaver,  and  Ellison.  All 
these,  however,  must  be  regarded  as  so  many  attempts  to 
correct  what  ought  not  to  exist.  If  the  velocity  of  wind 
is  not  checked  before  it  reaches  the  inside  of  the  room,  it 
is  then  too  late  to  manage  it  satisfactorily.  The  wind 
might  be  successfully  managed,  and  the  air  at  the  same 
time  be  freed  from  many  of  its  suspended  impurities,  by 
constructing,  outside  the  building  to  be  supplied,  large  air 
receptacles  supplying  the  inlets.  These  receptacles  would 
7 


60     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

serve  a  purpose  in  supplying  air  analogous  to  that  of  our 
large  reservoirs  in  supplying  water.  The  entrance  to 
these  receptacles  could  be  guarded  by  filters  for  abstract- 
ing suspended  impurities:  and  the  fluctuating  air  pressure 
due  to  the  wind  could  be  regulated  by  automatic  valves. 

Admitting  Air  at  the  Top. — When  a  room  is  situated 
so  as  to  make  the  admission  of  the  air  at  the  bottom  in- 
convenient, it  may  be  admitted  from  the  top.  Fig.  4 
represents  McKinnelPs  circular  tube,  which  is  probably 
the  best  arrangement  for  this  form  of  ventilation.  The 
heat  of  the  room  causes  the  air  to  rise  and  pass  out  at  the 
inner  tube,  as  indicated  by  the  arrows.  The  addition  of 
the  cowl  A  would  tend  to  promote  the  same  upward  cur- 
rent. The  partial  vacuum  thus  formed  will  be  filled  by 
the  outside  air  flowing  in  at  the  large  encircling  tube,  the 
action  of  which  would  be  further  promoted  by  the  addi- 
tion of  the  inverted  flange  B.  The  horizontal  flange  C, 
at  the  lower  extremity  of  the  inner  tube,  deflects  the  in- 
flowing air  along  the  ceiling,  distributing  it  before  it  falls 
to  mingle  with  the  warm  air  of  the  room. 

This  method  of  admitting  the  air  has  some  advantages. 
The  cold  air,  by  its  contact  with  the  warm  air  near  the 
ceiling,  becomes  warm  before  reaching  the  occupants  of 
the  room.  By  its  admission  through  a  tube  encircling 
the  warm  inner  tube,  the  inflowing  air,  if  cold,  becomes 
warm  by  contact.  This  tube  will  not  always  act  as  an 
outlet.  If  the  windows  are  opened,  cold  air  will  come  in 
from  below,  supplying  the  place  of  the  ascending  warm 
air,  which  will  then  pass  out  at  both  tubes,  making  them 
both  outlets. 

The  conditions  of  natural  ventilation  may  be  sum- 
marized briefly :  The  air  of  the  room,  made  warm  by 
artificial  means,  and  by  the  heat  of  bodies,  has  a  tendency 
to  rise  ;  that  it  may  pass  put  as  fast  as  vitiated,  this  ten- 


REGULATING  THE  DRAFT  OF  OPENINGS. 


Gl 


dency  must  not  be  resisted,  but  promoted  by  openings 
from  above  into  aspirating  cowls  or  chimneys.  Fresh  air, 
which  supplies  the  place  of  the  outgoing  air,  must  be  so 
admitted  as  to  facilitate  the  same  movement  by  utilizing 


02     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

its  power  to  push.  In  order  that  it  may  be  pure,  it  must 
be  taken  from  an  elevated  source  by  means  of  an  upright 
shaft.  The  regularity  of  the  supply  must  be  regulated 
by  properly  constructed  valves. 


CHAPTER  X. 

VENTILATION   BY   WINDOWS. 

THE  primary  office  of  windows  is  to  admit  light ;  but 
owing  to  a  lack  of  proper  provision  for  the  passage  of 
fresh  air,  they  must  also  serve  the  secondary  office  of 
ventilation.  It  has  already  been  shown  that,  where  ven- 
tilators exist,  they  are  usually  only  nominal,  their  size, 
position,  and  construction  making  their  utility  almost 
wholly  imaginary.  As  windows,  then,  in  school-houses 
already  existing,  are  our  only  source  of  fresh  air,  and 
furnish  us  the  only  means  that  we  may  soon  reasonably 
hope  for,  it  behooves  us  to  make  the  most  of  them. 
Where  the  means  are  meager,  their  skillful  manipulation 
becomes  still  more  a  necessity.  Generally  speaking,  win- 
dows are  poor  ventilators.  On  a  balmy  day  in  spring, 
when  the  sky  is  clear,  the  dust  having  been  laid  by  a 
light  shower,  and  a  gentle  zephyr  is  blowing,  all  the 
windows  may  be  raised  (or  dispensed  with  entirely),  and 
the  air  allowed  to  circulate  freely  through  the  room. 
Under  such  circumstances,  windows  are  the  best  pos- 
sible ventilators,  unless  it  were  possible  to  remove  the 
walls  also.  To  ventilate  a  room  on  such  a  day  re- 
quires little  forethought.  The  common  instinct  of  a 
school-girl  to  throw  open  a  window  is  all  the  art  or  phi- 
losophy which  the  case  requires.  But  when  the  bitter 


VENTILATION  BY  WINDOWS.  63 

winds  of  winter  are  blowing,  or  rain  or  snow  is  pelting 
one  side  of  the  house,  or  perhaps  clouds  of  dust  and 
smoke  are  rolling  toward  the  house,  the  case  is  different ; 
the  instinct  which  throws  up  a  window  to  escape  a  stifling 
atmosphere,  throws  it  down  again  to  escape  a  worse  evil. 

When  wind  has  any  of  the  disagreeable  accompani- 
ments above  mentioned,  the  windows  should,  when  possi- 
ble, be  opened  on  the  leeward  side.  The  aspirating  power 
of  the  wind  has  a  vacuum-forming  tendency  on  the  side 
opposite  its  direction  ;  the  air  will,  therefore,  if  windows 
be  opened  on  that  side,  flow  out  of  the  room,  and  suffi- 
cient air  to  supply  the  vacancy  thus  made  will  work  its 
way  through  cracks  and  crevices  on  the  windward  side. 

It  often  occurs  that  windows  are  all  on  one  or  two 
sides  of  the  room  ;  we  then  have  our  choice  between  the 
suffocation  of  closed  windows  or  braving  the  elements 
admitted  by  open  ones.  Where  the  only  windows  happen 
to  be  on  the  windward  side,  and  the  wind  must  be  ad- 
mitted, it  is  better  to  open  them  at  the  top.  The  wind 
will  blow  in,  forcing  some  of  the  impure  air  out. 

Just  where  the  outlets  will  be  can  hardly  be  guessed. 
About  half  of  the  openings  to  a  room,  when  there  is  move- 
ment of  the  air  through  them,  must  of  necessity  be  out- 
lets. Where  the  outlets  are  will  depend  upon  the  posi- 
tion of  the  inlets  and  the  freaks  of  the  wind.  A  single 
opening  will  sometimes  be  both  inlet  and  outlet  where 
shifting  cross-currents  are  irregularly  passing.  The  air 
which  thus  enters  will  in  some  measure  mix  with  the 
vitiated  air  of  the  room,  diluting  the  exhaled  poisons. 
The  air  which  is  forced  out  will  carry  with  it  some  of  the 
impurities  ;  the  amount,  however,  depending  on  local  and 
changing  conditions.  This  kind  of  ventilation  may  be 
likened  to  the  imperfect  blood-circulation  in  the  cold- 
blooded reptiles,  which  have  a  single  ventricle  for  both 


64:     VENTILATION  AND  WARMING  OF  S.CHOOL-BUILDINGS. 


pure  and  impure  blood,  which  is  sent  through  the  system 
in  a  mixed  state. 

The  force  of  the  wind  admitted  through  open  single 
windows  may  be  partially  checked  by  fastening  a  piece 
of  board  to  the  top  sash  and  extending  into  the  room  ob- 
liquely upward  so  as  to  retard  its  fall  on  the  heads  of  the 
pupils.  In  Fig.  5,  a,  the  arrows  show  the  direction  of 

FIG.  6. 


R 


the  air  deflected  upward  as  it  passes  into  the  room,  E,  by 
the  oblique  board,  a,  attached  to  the  upper  sash ;  Z>,  on  the 
other  side,  represents  a  board  fitted  between  the  casings  on 
the  window-stool,  and  serves  a  similar  function. 

No  set  rules  can  be  given  as  to  whether  windows  should 
be  opened  from  the  top  or  from  the  bottom.  This  will 
depend  entirely  upon  the  circumstances — upon  whether  a 
window  when  opened  is  intended  for  an  outlet  or  an  in- 
let. This  requires  close  observation  on  the  part  of  the 


VENTILATION  BY  WINDOWS. 


65 


teacher,  as  well  as  careful  study  and  an  intelligent  under- 
standing of  the  existing  conditions.  When  the  wind  is 
not  blowing,  all  the  windows  should  be  opened,  both  top 
and  bottom  ;  the  size  of  the  openings  being  regulated  to 
suit  the  temperature.  In  this  way  the  air  of  the  room,  if 
it  is  warmer  than  the  outside  air,  will  rise  and  pass  out  at 
the  top  ;  the  outside  air,  being  heavier,  will  flow  in  at  the 
bottom.  In  summer,  when  the  air  of  the  room  is  cooler 
than  that  on  the  outside,  the  current  will  be  reversed. 

When  the  internal  and  external  temperature  is  about 
equal,  and  when  no  wind  is  stirring,  the  windows  should 
be  opened  about  equally  from  above  and  below,  and  as 
wide  as  possible,  giving  diffusion,  the  only  means  for  ven- 
tilation which  is  under  the  supposed  conditions  existing, 
as  much  freedom  as  possible. 

It  is  when  the  wind  is  blowing  that  the  greatest  diffi- 
culty is  found  in  ventilating  by  windows,  but  by  skillful 

FIG.  6. 


management  much  more  can  be  done  toward  establishing 
a  constant  current  than  is  generally  supposed.  The  most 
favorable  condition  is  when  windows  are  on  opposite  sides 
of  the  room.  Fig.  6  supposes  this  case,  where  a  modcr- 


66     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

ate  wind  is  blowing  from  the  direction  indicated  by  the 
large  arrows.  By  opening  the  window  on  the  windward 
side  at  the  top,  and  the  one  on  the  leeward  side  at  the 
bottom,  a  current  is  established  as  indicated  by  the  large 
inside  arrows ;  this  direction  being  the  resultant  of  two 
forces — one  the  horizontal  force  of  the  wind,  the  other 
the  greater  specific  gravity  of  the  cold  air.  This  current, 
as  it  passes  through,  will  have  an  aspirating  power  to 
draw  the  air  of  the  other  parts  of  the  room  toward  it. 
This  is  simply  the  vacuum-forming  tendency  which  fluids 
always  possess  when  moving.  The  small  arrows  show  the 
direction  of  the  air  in  the  various  parts.  Now  if  the  win- 
dow at  D  be  slightly  raised,  and  the  one  at  C  slightly 
lowered,  the  vacuum-forming  tendency  within  will  initi- 
ate a  sufficient  current  through  these  openings  to  supply 
the  vacancy.  Admitting  the  cold  air  at  the  top,  and  let- 
ting the  foul  air  out  below,  seems  to  contradict  the  natu- 
ral theory  of  ventilation  as  before  described  ;  but  it  must 
be  remembered  that  here  the  force  of  the  wind  is  utilized 
instead  of  the  unequal  weights  of  columns  of  hot  and  cold 
air.  A  further  advantage  is  here  realized  in  the  cold  air 
being  warmed  before  it  strikes  the  occupants  of  the  room. 

It  more  frequently  occurs,  especially  in  school-houses 
containing  several  rooms,  that  the  only  windows  are  on 
two  adjacent  sides.  In  this  case  it  is  generally  best  to 
make  the  principal  top  openings  on  the  side  of  the  strong- 
est wind,  and  the  principal  bottom  openings  on  the  re- 
maining side.  The  wind  will  then  after  entering  be 
deflected  by  the  opposite  wall  in  the  direction  of  least  re- 
sistance, which  will  be  toward  the  largest  openings  on  the 
adjacent  side.  • 

When  windows  are  only  on  one  side  of  the  room, 
the  difficulty  is  still  further  increased.  In  this  case  it  is 
generally  better  to  make  the  principal  opening  at  the  top, 


VENTILATION  BY   WINDOWS. 


67 


and  a  smaller  one  at  the  bottom.  The  purpose  of  this  is 
illustrated  by  Fig.  7.  When  the  wind  is  very  strong,  the 
upward  tendency  of  the  inside  air  may  be  counteracted 


Fio.  7. 


by  a  large  opening  at  a.  The  air,  being  thus  forced  in, 
will  seek  the  lines  of  least  resistance  in  escaping.  By 
making  a  small  opening  at  B  it  will  become  an  outlet,  as 
it  has  less  to  oppose  than  at  a,  where  the  momentum  of  a 
large  inflowing  quantity  would  be  encountered.  From  the 
laws  of  fluid  pressure  it  would  at  first  appear  that  the 
tendency  of  the  outside  air  to  enter  at  B  would  be  as  great 
as  at  a,  and,  indeed,  even  more,  owing  to  the  greater 
depth  below  the  surface;  but,  when  it  is  remembered  that 
the  relative  friction  which  fluids  have  to  overcome  in 
passing  through  small  orifices  is  so  much  greater,  it  is 
plain  that  in  the  case  of  the  present  example  the  relative 
absence  of  friction  in  the  larger  top  opening  gives  to  the 
wind  when  passing  through  a  momentum  which  is  suffi- 
cient to  establish  the  current.  If,  however,  the  wind  is 
of  only  moderate  velocity,  the  current  will  be  likely  to  set 


68     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


the  other  way — will  enter  at  the  bottom,  and  pass  out  at 
the  top.  In  this  case  the  size  of  the  openings  must  be 
suited  to  the  temperature,  the  number  of  pupils  in  the 
room,  as  well  as  their  capacity  to  bear  hardship. 

When  the  wind  is  not  strong,  and  the  location  of  in- 
lets and  outlets  is  not  evident,  they  may  generally  be 
found  by  the  aid  of  a  feather  fastened  to  the  end  of  a 
pointer,  which,  held  in  front  of  an  opening,  will  indicate 
the  direction  of  the  passing  current. 

The  best  possible  window  ventilation  requires  the  use 
of  double  windows.  Ideal  window  ventilation  would  re- 
quire double  windows  on  four  sides  of  the  room.  Such 
conditions  would  afford  a  fair  degree  of  purity.  By  means 
of  double  windows  the  wind  may  be  admitted  or  kept  out 
when  and  where  desired.  Its  force  could  be  broken  by 

FIG.  8. 


R 


ff 

v  S 


being  made  to  pass  perpendicularly  between  the  windows 
before  entering  the  room.  Inlets  and  outlets  could  be 
made  at  the  top  or  bottom  as  required  by  the  circum- 
stances, and  the  strong  drafts  unavoidable  in  single  win- 
dows avoided.  Fig.  8  illustrates  a  single  case,  which,  of 


VENTILATION   BY   WINDOWS. 


69 


course,  permits  of  indefinite  modification  to  suit  existing 
circumstances  and  changing  conditions.  Here  the  air 
enters  at  A  by  the  upper  outer  window  being  lowered ; 
descending,  it  enters  the  room  at  B,  by  the  inner  lower 
sash  being  raised;  passing  over  the  heater  H,  it  is  warmed 
before  striking  the  pupils ;  rising,  it  passes  through  the 
room,  and  escapes  at  C,  by  both  inner  and  outer  windows 
being  lowered. 

Suppose  another  case,  that  of  a  stove  situated  in  the 
middle  of  the  room.    Fig.  9  illustrates  an  instance  where 

FIG.  9. 


a  single  opening  serves  both  as  inlet  and  outlet.  By 
making  large  openings  at  A  c  and  B  D,  by  lowering  tho 
outside  windows  and  raising  the  inside  ones ;  and  the 
smaller  openings,  a  and  b,  by  slightly  lowering. the  inside 
windows,  it  is  possible  to  divide  the  cold  and  hot  air  cur- 
rents, as  indicated  by  the  arrows — the  chief  controlling 
principle  here  being  the  unequal  weight  of  hot  and  cold 
air.  Without  multiplying  instances,  suffice  it  to  say  that 
in  window  ventilation  the  place  and  relative  size  of  open- 
ings must  be  conditioned  by  the  direction  of  the  wind, 
the  velocity  of  the  wind,  and  the  position  of  the  heater. 


70     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 
CHAPTER  XI. 

ARTIFICIAL  VENTILATION. 

As  distinguished  from  so-called  natural  ventilation, 
where  the  air  is  changed  by  means  of  doors  and  windows, 
or  other  openings,  the  moving  forces  being  the  wind  and 
the  unequal  weights  of  hot  and  cold  air,  certain  additional 
or  artificial  means  may  be  used  whereby  the  change  of  air 
may  be  made  to  take  place  more  rapidly,  and  the  regu- 
larity of  the  movement  more  certain,  than  is  possible  in 
natural  ventilation. 

The  changes  of  temperature  both  in  frequency  and 
amount  are  in  this  country  so  marked,  and  the  direction 
and  velocity  of  the  wind  so  various  and  fickle,  that  even 
the  most  carefully  worked  plans  for  the  use  of  the  natural 
methods  above  described  are  attended  with  constant  em- 
barrassment and  partial  defeat. 

Something  has  been  done  toward  an  intelligent  solu- 
tion of  the  all-important  problem  of  how  to  measure  out, 
warm,  and  furnish  to  the  occupants  of  crowded  rooms  air 
of  the  proper  quantity  and  quality;  but  the  subject  has 
not  received  a  tithe  of  the  attention  that  its  merits  de- 
mand. To  know  exactly  how  much  air  is  needed  by  a 
school,  and  to  furnish  it  by  exact  mechanical  measure- 
ment, is  not  a  very  severe  problem,  and  is  one  with  which 
the  designers  of  buildings  should  be  familiar.  To  meas- 
ure the  amount  of  water,  and  estimate  its  velocity,  which 
is  necessary  to  do  a  certain  amount  of  work,  is  a  problem 
of  every-day  experience  with  the  civil  engineer.  Now  air, 
no  less  than  water,  is  matter,  and  subject  to  nearly  the 
same  laws  of  weight,  motion,  and  measurement ;  and  to 
manipulate  it  in  the  manner  required  by  the  conditions 
and  necessities  of  ventilation,  providing  at  the  same  time 


ARTIFICIAL  VENTILATIOX.  71 

for  its  exigencies,  is  an  element  in  school-house  construc- 
tion plainly  possible,  and  should  be  recognized  as  a  part 
of  the  duty  of  him  who  is  intrusted  with  this  important 
function.  It  is  as  easy  to  measure  air  as  to  measure  any 
other  substance ;  and,  owing  to  its  extreme  mobility,  its 
movement  is  effected  more  easily  than  most  other  matter. 

The  different  ways  by  which  this  movement  may  be 
effected  may  be  conveniently  considered  under  two  gen- 
eral heads — the  vacuum  movement  and  the  plenum  move- 
ment. 

TJie  Vacuum  Movement — Aspirating  Chimneys. — The 
act  of  animal  respiration  is  a  pumping  or  vacuum-forming 
process.  As  the  respiratory  cavity  is  enlarged  by  muscu- 
lar effort,  the  air  rushes  in  to  fill  the  vacancy  thus  made. 
Chimneys  which  serve  the  purpose  of  removing  smoke 
from  a  fire,  or  the  foul  air  from  a  room,  are  therefore 
called  aspirating,  because  they  imitate  in  a  certain  way 
the  breathing  out  of  the  internal  impurities. 

The  vacuum-forming  power  in  chimneys,  instead  of 
muscular  action,  is  the  expanding  power  of  heat,  which 
lightens  the  air  in  the  chimney  when  the  outside  heavier 
air  pushes  it  upward.  The  use  of  the  aspirating  chimney 
is  evident.  It  is  plain  that  if  the  air  of  a  room  has  com- 
munication with  a  chimney  by  an  opening  leading  into 
it  where  the  air  is  hot,  rare,  and  rising,  it  will  be  drawn 
out  and  up  to  the  outside  air. 

The  velocity  of  the  air-currents  produced  by  natural 
ventilation,  described  above,  can  by  this  means  be  greatly 
augmented.  The  utility  of  downcast  shafts  for  the  pur- 
pose of  securing  pure  air  is  in  ordinary  natural  ventilation 
greatly  lessened  by  the  friction  which  air  encounters  in 
passing  through  them :  so  much  so,  indeed,  that  they 
sometimes  have  to  be  discarded,  being,  when  the  friction 
is  in  excess  of  the  drawing  power,  obstructionists  instead 
8 


72     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

of  promoters  to  ventilation.    By  the  use  of  the  aspirating 
chimney  this  difficulty  may  be  overcome. 

In  Fig.  10,  the  fire  on  the  grate  Gr  produces  an  upward 
current  through  the  chimney  D.      This  draws  the  air 

FIG.  10. 


from  the  tube  E,  into  which  the  foul  air  of  the  room  flows, 
through  the  openings/.  The  partial  vacuum  thus  formed 
in  the  room  causes  the  air  to  flow  down  the  shaft  B.  The 
downward  and  upward  cast  cowls,  a  and  c,  described 
above,  aid  further  in  facilitating  the  movement.  The 


ARTIFICIAL  VENTILATION.  73 

figure  is  only  intended  to  illustrate  the  principle.  The 
details  must,  of  course,  be  modified  in  each  case  to  suit 
circumstances,  without  violating  any  of  the  laws  which 
give  to  the  aspirating  chimney  its  main  value. 

The  main  principles  which  the  figure  illustrates  are : 
the  air  is  taken  from  an  elevated  source,  it  is  admitted 
below,  and  is  distributed  around  the  room.  It  rises  and 
passes  out  naturally  at  the  top  of  the  room  into  the  par- 
tial vacuum  made  in  the  chimney  by  the  heat  from  the 
fire  at  Gr.  The  tube  E  is  sometimes  carried  down  to  the 
base  of  the  chimney  before  entering  it ;  the  object  of  this 
being  to  prevent  the  reflux  of  smoke  sometimes  resulting 
from  sudden  changes  of  conditions,  as  the  wind,  rapid 
lowering  of  the  temperature,  etc.,  producing  a  temporary 
reversal  of  the  current  down  the  chimney.  This  may  be 
effectually  prevented  by  adjusting  at  the  aperture  H  a 
valve  v  opening  toward  the  chimney.  This,  when  unin- 
fluenced by  currents,  should  hang  naturally,  closing  the 
aperture  by  its  own  weight,  yielding  readily  to  a  slight 
pressure  of  a  current  from  the  direction  of  the  room,  and 
closing  effectually  against  a  pressure  from  an  opposite 
current,  thus  shutting  off  the  smoke  resulting  from  down 
draught.  This  method  of  removing  the  foul  air  was  first 
put  in  successful  practice  by  Dr.  Reid  in  his  class-room  in 
Edinburgh.  The  English  House  of  Commons  is  venti- 
lated on  the  same  principle. 

There  are  other  advantages  in  carrying  the  foul-air 
tube  directly  into  the  chimney  instead  of  carrying  it  down- 
ward. The  friction  resulting  from  lengthening  the  tube, 
and  the  inclusion  of  two  more  elbows,  would  materially 
lessen  the  draught;  furthermore,  it  has  been  proved  by  ex- 
periment that  the  draught  in  a  chimney  is  greatest  near  the 
top,  directly  under  the  roof.  This  may  be  due  partly  to 
the  increased  velocity  of  the  hot  air  in  the  chimney  near 

4 


74     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

the  top,  caused  by  an  upward  acceleration  acquired  in 
rising,  and  partly  to  diminished  resistance  to  the  air  as 
it  nears  its  point  of  release  from  the  confining  walls  of 
the  chimney. 

It  may  at  first  appear  contrary  to  known  laws  that  the 
velocity  of  a  rising  column  of  air  should  be  accelerating, 
but  a  moment's  consideration  will  be  sufficient  to  under- 
stand the  paradox.  Acceleration  will  always  occur  when 
a  body  free  to  move  is  acted  upon  by  a  constant  sufficient, 
as  the  action  of  gravity  on  falling  bodies. 

The  space  passed  over  in  unit  time,  taken  at  any  period 
of  a  body's  movement,  will  be  measured  by  the  initial 
velocity  due  to  the  constant,  plus  the  velocity  previously 
acquired.  Now,  a  body  which  has  a  tendency  to  rise  will 
accelerate  so  long  as  the  tendency  is  constant.  Thus,  a 
cork,  or  other  light  body,  in  rising  from  a  great  depth  in 
water,  would  have  a  greater  velocity  when  near  the  surface 
than  when  it  first  began  to  rise.  The  cause  of  its  rise 
is  the  difference  between  the  pressures  on  its  upper  and 
lower  surfaces,  but  as  this  difference  is  always  the  same, 
whether  at  a  great  depth  or  near  the  surface,  it  is  a  con- 
stant which  augments  at  every  instant  the  velocity  already 
attained. 

Montgolfier's  formula,  v  =  \/%gh,  is,  under  the  sup- 
posed conditions,  as  true  of  rising  as  of  falling  bodies — 
remembering  that  g,  instead  of  being  32  feet,  now  repre- 
sents the  distance  the  body  would  rise  the  first  second. 
This  would,  of  course,  depend  on  the  specific  gravity  of 
the  substance,  and  would  need  be  determined  experiment- 
ally. The  case  of  the  air  in  the  chimney  is  a  little  differ- 
ent from  the  one  supposed,  unless  it  be  that  the  source  of 
the  heat  be  equally  distributed  along  the  whole  length  of 
the  chimney.  When  the  source  of  heat  is  as  usual  at  the 
bottom,  each  particle  of  air  loses  some  of  its  heat,  and 


ARTIFICIAL  VENTILATION.  75 

therefore  some  of  its  tendency  to  rise  in  passing  out ;  but 
the  retardation  due  to  this  cause  is  slight  in  comparison 
with  the  momentum  which  has  been  stored  up  by  previous 
impulses.  Even  this  loss  of  heat  may  not  occur  if  we  are 
to  credit  the  testimony  of  practical  architects.  E.  E. 
Rice,  of  Washington,  inventor  of  a  system  of  ventilation, 
says  :  "I  find  in  practice  the  highest  temperature  imme- 
diately below  the  level  of  the  roof."  If  this  be  true,  it 
furnishes  still  further  reason  for  upward  acceleration. 

In  some  systems  of  heating  and  ventilating  now  in 
use  the  foul-air  tubes  are  carried  down  and  admitted  to 
the  chimney  beneath  the  fire.  It  might  at  first  seem  that 
this  arrangement  would  give  a  stronger  draught,  on  ac- 
count of  the  fact  that  this  air  is  depended  upon  to  supply 
the  combustion  in  the  chimney,  but  when  wholly  de- 
pended upon  for  this  purpose  the  fire  will  lack  much  of 
that  vigor  of  combustion  upon  which  the  aspirating  power 
of  the  chimney  will  mainly  depend.  Air  which  has  already 
been  robbed  of  much  of  its  oxygen,  and  been  contaminated 
with  the  products  of  respiration,  is  a  poor  supporter  of 
combustion.  It  appears,  therefore,  that  in  order  to  give 
the  chimney  its  greatest  aspirating  power,  the  fire  should 
be  fed  with  pure  air.  It  is  as  poor  economy  to  feed  a  fire 
with  C02  as  to  feed  pupils  with  it.  Whatever  intensifies 
the  fire  increases  the  draught. 

The  power  of  a  strong  upward  current  of  air  in  a 
chimney  to  abstract  air  from  tubes  opening  into  it  will 
be  better  appreciated  by  remembering  that  some  of  the 
most  effective  air-pumps  are  constructed  on  precisely  this 
principle.  An  almost  perfect  vacuum  can  be  made  in  a 
vessel  leading  by  a  tube  to  another  tube  through  which  a 
column  of  water  is  falling.  In  Bunsen's  pump,  con- 
structed on  this  principle,  water  is  used  ;  and  in  Spren- 
gel's,  mercury.  In  an  aspirating  chimney  the  moving 


76     VENTILATION  AND  WARMING  OP  SCHOOL-BUILDINGS. 


current  is  gaseous  instead  of  liquid,  and,  although  less 
effective,  is  sufficiently  so  to  create  a  powerful  draught. 
In  view  of  this  fact,  it  might  be  better  in  a  house  above 
one  story  to  carry  all  the  ventilating  tubes  to  a  main  tube 
extending  up  nearly  to  the  roof  before  opening  into  the 
chimney. 

Owing  to  the  fact  that  the  momentum  of  columns  of 
air  is  proportional  to  their  volume,  aspirating  chimneys 
should  be  built  as  high  as  convenient.  Where  buildings 
are  heated  by  steam,  the  draught  in  aspirating  chimneys 
may  be  created  by  carrying  steam  jets  into  them ;  the 
escaping  steam  causing  a  partial  vacuum,  which  is  filled 
by  air  coming  from  below  toward  the  direction  taken  by 
the  steam.  See  Fig.  11,  where  C  represents  the  aspirating 
chimney,  B  the  boiler,  F  the  furnace,  L>  the  air-duct. 

FIG.  11. 


M 


The  arrows  show  the  direction  of  the  current.  The  steam 
thus  issued  into  a  chimney  will  set  in  motion  a  body  of 
air  about  217  times  its  own  bulk.  When  steam  is  used, 


ARTIFICIAL  VENTILATION.  77 

the  foul-air  tubes  would  perhaps  better  be  placed  below 
the  jets,  as  it  would  in  this  case  be  no  interference  to  com- 
"bustion,  and  the  chief  vacuum  -  producing  power  is,  in 
this  case,  where  the  steam  is  escaping. 

In  buildings  furnished  with  burning-gas,  a  few  jets 
kept  burning  in  a  chimney  are  often  sufficient  to  produce 
the  requisite  draught.  In  summer  this  will  be  all-suffi- 
cient. General  Morin  found  that  one  cubic  foot  of  gas  is 
sufficient  to  set  in  motion  1,000  cubic  feet  of  air. 

Where  buildings  are  heated  by  steam,  it  is  better  to 
run  a  coil  of  steam-pipe  into  the  base  of  the  shaft.  The 
following  formula,  deduced  by  Prof.  W.  P.  Trowbridge, 
may  be  found  useful  for  determining  the  amount  of 
steam-pipe  necessary  to  be  put  at  the  base  of  an  aspirat- 
ing chimney  in  order  to  maintain  the  desired  draught  : 

Tirrri 

S  =  TfTm  —  ^-rX  1,500,  where  S  =  number  of  square  feet 

' 


in  exterior  surface  of  the  coil  at  the  base  of  the  chimney; 
Ta  =  absolute  temperature  of  the  external  air—  that  is, 
the  common  or  thermometric  temperature  plus  459  '4°;* 
W  =  weight  of  air  in  pounds  which  is  discharged  in  1 
second  ;  H  =  height  of  flue  ;  Ts  =  absolute  temperature 
of  the  steam  in  the  pipe.  The  constant  1,500  is  deter- 
mined from  other  constants  which  were  employed  in  de- 

*  The  absolute  temperature  is  obtained  from  the  relations  which  ex- 
ist between  the  temperature  of  a  body  and  its  rate  of  expansion.  If  air 
at  0°  C.  be  heated,  its  volume  will  be  increased  -^rs  of  its  original  vol- 
ume for  every  degree  raised.  Then  its  volume  will  be  doubled  when 
273°  is  reached.  If  it  be  cooled  below  0°,  its  volume  will  be  diminished 
yfj  for  every  degree  lowered.  If  this  diminution  should  proceed  at  the 
same  ratio  till  —  273°  is  reached,  its  volume  would  be  nothing.  This  is, 
of  course,  true  only  theoretically,  as  it  is  impossible  to  freeze  matter  out 
of  existence.  But  this  point  is  taken  as  absolute  zero,  which  when  used 
makes  all  temperatures  positive.  Reduced  to  the  Fahrenheit  scale,  it  is 
459-4°. 


78     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

ducing  the  formula ;  they  were  :  the  force  of  gravity, 
specific  heat  of  air,  ratio  of  transfer  of  heat  to  air  by 
coils,  and  the  ratio  between  the  theoretical  and  actual 
Telocity  in  the  flue. 

Steam-coils  are  used  for  the  purpose  here  named  in 
Columbia  College,  New  York,  where  the  heating  and  ven- 
tilating apparatus  was  arranged  by  Prof.  Trowbridge. 
They  are  also  used  in  the  Johns  Hopkins  University  of 
Baltimore. 

It  is  always  best  when  possible  to  have  the  ventilating- 
flue  combined  with  the  smoke- chimney,  so  as  to  utilize 
the  heat  of  the  waste  products  of  combustion.  When 
heat  from  this  source  is  insufficient,  it  can  be  supple- 
mented by  the  use  of  the  steam-coils. 


CHAPTER  XII. 

THE  MOVEMENT  OF  TFE  AIE  BY  MECHANICAL  MEANS. 

The  Vacuum  Movement. — A  current  of  air  through  a 
room  for  the  purpose  of  ventilation  is  sometimes  produced 
by  putting  into  the  ventilating  or  foul-air  duct  an  extract- 
ing fan,  Archimedean  screw,  pump,  or  blower.  Such  an 
arrangement  may  take  the  place  of  an  aspirating  chimney, 
or  by  being  put  into  the  chimney  become  a  part  of  it,  sup- 
plementing its  draught-producing  function.  The  func- 
tion of  mechanical  propellers,  when  put  in  the  foul-air 
duct,  is  always  the  same,  that  of  producing  a  partial 
vacuum  in  the  room  by  extracting  the  foul  air,  thus 
making  room  for  a  fresh  supply,  which  will  find  its  way 
in  by  openings  provided  for  that  purpose. 

When  mechanical  means  are  thus  made  use  of,  it  of 


MOVEMENT  OF  THE  AIR  BY  MECHANICAL  MEANS.   79 

course  makes  no  difference,  in  the  rapidity  of  change 
which  the  air  in  the  room  will  undergo,  whether  the  pro- 
peller be  placed  in  the  foul-air  duct  and  draws  the  air 
through  the  room,  or  whether  it  be  placed  in  the  fresh- 
air  duct  and  pushes  the  air  through  the  room,  for  in 
either  case  the  propeller  moves  the  same  quantity  of  air. 

Whatever  is  forced  in  must  find  a  way  out,  and  what- 
ever is  drawn  out  must  be  supplied  by  inlets.  When  air 
is  thus  drawn  out,  it  is  a  vacuum-forming  process,  and 
the  pressure  of  air  on  the  inner  parts  of  the  room  will  be 
somewhat  less  than  that  on  the  outside.  Currents  of  air, 
therefore,  through  small  openings,  cracks,  windows,  as 
also  from  halls,  closets,  etc.,  will  be  inward  ;  the  quality 
of  the  air,  therefore,  will  be  determined  by  the  character 
of  the  inlets,  and  the  function  of  the  intended  inlets  may 
be  usurped  by  an  open  door  delivering  air  too  cold,  an 
open  closet  delivering  impure  air,  or  an  elevated  crack  or 
other  opening  delivering  air  too  high  up  to  be  utilized, 
and  so  drawn  out  unused. 

Another  objection  to  this  manner  of  drawing  the  air 
through  the  room,  especially  where  the  draught  is  from 
several  rooms,  is  that  the  draught  will  not  be  equal.  In 
rooms  which  have  their  inlets  through  tubes  compara- 
tively short,  where  the  incoming  air  encounters  very  little 
friction,  the  supply  will  be  ample  and  at  the  expense  of 
more  remote  rooms  to  which  the  air  must  pass  through 
long  tubes  and  perhaps  pass  abrupt  angles.  The  relative 
draught  will  also  fluctuate  with  changes  in  the  force  and 
direction  of  the  wind,  sometimes  favoring  one  side  of  the 
house,  sometimes  another. 

The  Plenum  Movement. — Instead  of  drawing  the  foul 
air  from  the  room  by  placing  the  propeller  in  the  exit 
shaft,  the  pure  air  may  be  forced  in  by  placing  the  pro- 
peller in  the  inlet  duct.  This  may  be  called  the  plenum 


80     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

movement,  and  produces  in  the  room  a  perflating  instead 
of  a  vacuum-forming  tendency. 

The  plenum  has  many  advantages  over  the  vacuum 
movement.  In  this  movement  the  atmospheric  fullness 
in  the  room,  produced  by  perflation,  causes  all  currents 
through  accidental  openings  to  be  outward  instead  of 
inward,  thus  preserving  the  air  of  the  room  from  the 
incidental  external  impurities  of  closets,  cellars,  base- 
ments, etc. 

The  plenum  movement  has  not  received  the  attention 
which  its  usefulness  demands.  Much  as  may  be  said  in 
favor  of  natural  ventilation,  and  evident  as  it  is  that  all 
successful  ventilation  must  depend  on  a  studious  and 
skillful  conformity  to  the  few  natural  laws  underlying 
the  whole  process,  it  will  still  remain  questionable,  after 
everything  possible  has  been  done  to  produce  draught 
by  differences  of  height  and  temperature,  whether  it 
is  possible  to  supply  at  all  times  a  large  school-house 
full  of  pupils  with  air  of  the  necessary  quantity  and 
quality. 

We  have  seen  in  preceding  pages  how  fast  air  must 
pass  through  a  room  in  order  to  supply  the  'requirements 
of  respiration.  We  have  also  seen  that  this  current  must 
be  properly  distributed  and  be  of  a  certain  temperature 
and  humidity.  Now  these  conditions  are  approached  in 
different  degrees  by  different  systems  of  heating  and  ven- 
tilating ;  but  in  no  system  has  the  ideal  been  reached 
without  the  aid  of  mechanical  means. 

There  are  many  good  systems  now  in  use,  the  in- 
ventors of  which  deserve  great  credit  for  much  good 
work  toward  solving  the  great  problem  of  warming  and 
ventilating.  But  the  efficiency  of  none  of  these  systems 
is  quite  commensurate  with  the  claims  of  their  inventors. 
The  comparative  merits  of  some  of  the  best  systems  now 


MOVEMENT  OF  THE  AIR  BY  MECHANICAL  MEANS.  81 

in  use  are  discussed  in  another  place,  where  the  prin- 
ciples involved  in  each  are  examined. 

The  assertion  which  I  here  venture,  that  perfect 
warming  and  ventilating  has  not  been  attained  without 
the  aid  of  mechanical  means,  is  easily  demonstrated  on 
general  principles.  What  is  implied  in  perfect  ventila- 
tion ?  As  an  example  of  it,  we  might  suppose  the  case 
of  a  balmy  spring  day,  when  a  gentle  breeze,  barely  per- 
ceptible, is  passing  through  the  wide-open  opposite  win- 
dows of  a  room  situated  in  a  salubrious  locality.  In  this 
case  the  air  is  of  a  genial  warmth.  It  has  not  been  blown 
across  a  burning  desert  or  through  an  artificial  furnace. 
It  does  not  enter  the  room  scorching  hot,  where  it  mixes 
with  other  air  icy  cold.  It  is  not  kept  in  the  room  till  it 
has  become  dangerously  impure  ;  but  in  passing  directly 
through  it  gathers  the  impurities  of  the  passing  breath 
and  carries  them  away  as  fast  as  formed,  leaving  the 
room  while  still  in  a  state  of  respirability. 

Now  this  may  be  produced  artificially,  by  warming 
the  air  to  the  proper  temperature  and  forcing  it  through 
the  room  by  mechanical  means,  but  by  any  other  means 
now  in  use  it  is  impossible.  A  little  reflection  will  make 
this  plainly  evident. 

We  have  previously  seen  that  when  adequate  ven- 
tilation is  maintained  by  an  upward  current  through 
the  room,  it  is  caused  mainly  by  the  difference  between 
the  internal  and  external  temperatures  and  the  vacuum- 
producing  power  of  aspirating  chimneys.  But  how  is 
this  difference  of  temperature  in  very  cold  weather  to  bo 
produced  ?  If  by  stoves,  the  temperature  in  different 
parts  of  the  room  will  be  unequal — some  parts  hot,  and 
other  parts  cold  ;  if  by  the  direct  radiation  of  steam 
pipes,  the  entering  air  is  cold,  and,  although  it  be  warmed 
by  passing  over  the  heater,  it  will  be  warmed  unequally 


82     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

and  imperfectly.  If  by  warm  air  entering  the  room,  it 
must  enter  fast  enough  to  change  the  air  in  the  room 
about  every  seven  minutes ;  but  air  of  this  temperature 
will  not  enter  thus  rapidly  by  any  ordinary  medium  of 
pipes  and  tubes,  on  account  of  friction,  etc. 

The  main  cause  of  the  inflow  of  the  warm  air  is  the 
difference  of  its  specific  gravity  due  to  heat.  For  the 
inflow  to  be  rapid  the  heat  must  be  great,  but  hot  air 
must  be  ruled  out  of  the  legitimate  conditions  of  perfect 
ventilation.  It  is,  I  think,  possible  to  pass  air  not  above 
a  temperature  of  genial  warmth  when  it  enters,  in  suffi- 
cient quantities  to  serve  the  ends  of  ventilation,  and 
sufficiently  to  warm  the  room  in  cold  weather,  but  it  re- 
quires a  different  arrangement  of  pipes  and  furnaces  than 
has  yet  been  put  in  practice,  and  might  exceed  in  cost  a 
good  plenum  movement. 


CHAPTEE  XIII. 

AIR-PKOPELLERS. 

THE  problem  of  setting  in  motion  quantities  of  air 
sufficient  to  supply  the  requirements  of  ventilation,  and 
to  so  direct  this  air  as  to  approximate  a  maximum  of 
movement  with  a  minimum  of  expended  power,  is  a  me- 
chanical problem  which  becomes  important  in  considering 
the  plenum  movement,  both  from  the  standpoint  of  work 
accomplished  and  the  economy  of  accomplishing  it. 

Of  propellers  for  moving  air,  many  kinds  have  been 
used,  among  which  may  be  mentioned  those  of  Combs, 
Kittenger,  Hales,  Letoret,  Howorth,  Eoots,  Glepin,  Ar- 
nott,  Chaplin,  Perrigault,  Lloyd,  Fernie,  Hendry,  Hope, 


AIR-PROPELLERS.  83 

and  Blackman.  Most  of  these  are  in  some  form  of  revolv- 
ing  fan,  the  floats  of  which  are  so  placed  as  to  set  in  motion 
the  air  outward  radially,  thereby  creating  a  partial  vacuum 
near  the  axis,  thus  setting  more  air  in  motion  as  it  is  filled. 
The  object  of  a  propeller  is  not  only  to  set  in  motion 
large  quantities  of  air,  but  to  set  it  in  motion  in  such  a 
manner  as  not  to  produce  loss  by  opposing  counter  cur- 
rents and  by  useless  friction.  Air,  on  account  of  its  ex- 
treme mobility,  requires  primarily  very  little  power  to 
move  it,  but  when  it  is  forced  through  small  apertures, 
or  set  in  motion  in  such  a  way  as  to  produce  cross  cur- 
rents, great  power  may  be  required  to  accomplish  a  little 
work.  Dr.  Arnott  observed  this  in  the  working  of  re- 
volving fans,  and  invented  a  ventilating  pump  which  he 
put  in  operation  in  a  hospital.  So  conserved  was  the 
power  by  the  construction  of  his  propeller  that  the  entire 
building  was  supplied  with  air  by  the  motive  power  de- 
rived from  the  descent  of  the  water  used- in  the  building 
from  a  high  reservoir  to  the  basement.  It  may  be  re- 
marked here  that  everything  which  Dr.  Arnott  devised  for 
the  improvement  of  ventilation  possessed  singular  and 
unusual  merit.*  Since  Dr.  Arnott's  time,  however,  con- 
siderable improvement  has  been  made  in  revolving  fans 
and  other  propellers. 

*  As  before  mentioned,  Dr.  Arnott  never  secured  the  exclusive  right 
to  his  inventions  by  letters  patent,  but  in  a  true  philanthropic  spirit 
gave  the  results  of  his  labors  to  the  world.  It  is  douttful,  however, 
whether  this  did  not  hinder  rather  than  promote  the  propagation  of  his 
ideas.  It  is  noteworthy  that  while  these  inventions  are  acknowledged  to 
be  superior  to  most  others,  and  are  free  to  everybody,  they  have  been 
comparatively  little  used.  Had  the  worthy  author  secured  his  inventions 
by  letters  patent  everybody  would  be  ready  to  scrutinize  their  merits  and 
pay  the  price  ;  but  when  a  gift  is  offered  it  is  little  regarded,  so  prone 
is  human  nature  to  think  it  impossible  for  a  man  to  give  away  that  which 
is  of  value. 
9 


84     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


The  objection  which  has  heretofore  been  made  to  the 
plenum  movement  is  its  expense.  Owing  to  the  extreme 
mobility  of  air,  the  power  required  in  merely  moving  it  is 
theoretically  almost  nothing ;  the  expense,  then,  must 
result  from  the  manner  of  moving  it — from  forcing  it 
through  small  apertures,  and  from  friction  and  collision 
due  to  misdirecting  it.  The  construction  of  the  machines 
for  propulsion  is,  therefore,  of  so  much  importance  in 
the  economy  of  mechanical  ventilation  that  I  shall  notice 
at  some  length  the  construction  and  efficiency  of  some  of 
the  earlier  and  later  types  of  revolving  propellers. 

Rittenger's  Fan. — Fig.  12  represents  Kittenger's  fan. 
A  is  a  side  view  showing  the  shell  y,  which  is  of  the  form 


FIG.  12. 


B 

6. 


\ 


\ 


of  an  Archimedean  spiral,  beginning  at  e ;  the  radius  of 
the  inlet  r2,  the  outer  and  inner  radii  of  the  vanes  r  and 
r1,  the  radii  I  of  the  curve  of  the  vanes ;  the  angle  z°  be- 
tween the  radius  and  the  initial  line  of  the  vane.  B  is  a 
section  on  the  line  xx'.  The  arrows  show  the  direction 
of  the  current, 


AIR-PROPELLERS.  85 

The  construction  of  this  fan  shows  that  its  design  is, 
first,  by  the  angle  z,  to  produce  a  motion  of  the  air  ra- 
dially, producing  a  vacuum-forming  tendency  at  the  cen- 
ter, causing  the  air  to  be  pushed  in  toward  that  point 
from  the  outside ;  and,  second,  by  curving  the  vanes 
forward,  to  direct  the  tangential  motion  of  the  air  as  far 
as  possible  toward  the  outlet  duct. 

To  understand  the  action  of  the  vanes  on  the  air,  sup- 
pose a  single  particle  of  air  at  p  struck  by  the  vane  as  it 
reaches  that  point  in  its  revolution.  If  the  angle  z°  were 
0,  then  the  particle  would  be  impelled  forward  on  the 
tangent  p'  p',  but  as  the  angle  z°  increases,  the  direction 
taken  by  p  will  be  more  radial,  the  amount  of  this  change 
of  direction  being  proportional  to  the  sine  of  z°,  the  rela- 
tion holding  between  0  and  90°.  If  the  vanes  be  straight, 
increasing  z  will  give  the  air  a  receding  tendency  ;  this 
the  curve  is  intended  to  prevent.  Now,  the  nature  of 
this  curve  is  of  course  important.  Its  radius  of  curvature 

r"  —  r  * 
is  expressed  by  Rittenger  by  the  formula  I  = = — 1— ^, 

where  r  —  outer  radius  of  the  vanes,  r,  =  inner  radius  of 
the  vanes,  z°  =  the  angle  between  the  radius  and  the 
initial  line  of  the  vane,  and  I  =  radius  for  the  curvature 
of  vanes.  The  formula  shows  that  as  the  vanes  are  nar- 
rowed, or  as  r1  —  r*  is  diminished,  I  will  decrease.  Refer- 
ence to  the  figure,  with  a  little  mechanical  conception, 
will  prove  the  general  correctness  of  these  relations.  For, 
if  we  imagine  r1  to  be  increased,  thus  narrowing  the  fan, 
the  particle  of  air  p  will  have  its  distance  from  the  shell 
diminished,  so  that  when  deflected  radially  by  increasing 
z°  it  would  have  a  sharper  curve  to  give  it  the  required 
forward  impulse  than  when  it  started  from  a  greater  dis- 
tance, giving  more  time  for  deflection. 

The  formula  shows,  further,  that  as  sine  z°  (or  z°)  is 


86     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

increased  I  will  be  diminished.  Referring  to  the  figure 
again,  the  reason  becomes  evident.  For  as  z°  is  increased 
the  particle  of  air  p  will  be  deflected  more  radially  ;  to 
counteract  this  before  the  circumference  is  reached  the 
curve  must  be  made  sharper — I  must  be  lessened. 

The  effect  which  in  this  fan  is  realized  in  practice  is 
about  forty  per  cent  of  the  power  expended.  Yet  this  is 
one  of  the  best  fans  which  have  been  thoroughly  tested. 
Surely  there  is  an  open  field  in  the  economy  of  applied 
power  for  the  mechanical  engineer. 

In  this  fan,  it  appears  to  me  that  much  of  the  loss  of 
effect  comes  from  beating  the  air  too  much  radially,  and 
not  enough  tangentially ;  or,  rather,  that  the  radial  and 
tangential  forces  are  not  properly  distributed.  In  this 
case  the  direction  of  the  impulses  is  too  much  outward 
on  the  shell,  and  not  enough  forward  toward  the  duct. 
Now,  this  can  be  partially  corrected  in  making  the  curve 
of  the  vane  elliptical  instead  of  circular,  where  each  vane 

comprises  one  fourth  of  the  ellipse.  I  would  therefore 

fr* r  *\  e 

propose  the  following  modified  formula  :  I  =  ^ .  0> 

2  rl  sine  * 

where  I  =  semi-major  axis  of  the  ellipse,  e  =  the  ratio  be- 
tween the  major  and  minor  axes,  and  r,  r,,  and  z°  =  same 
as  in  the  preceding.  This  relation  shows  that  e  increases 
with  the  width  of  the  vanes,  and  also  with  the  length  of 
the  semi-diameter  of  the  curve. 

The  amount  of  work  which  is  required  to  deliver  any 
given  amount  of  air  by  means  of  fans  may  be  calculated 

62-5       100 

by  the  formula  Hp.  =  — -  X X  V  h,  where  Hp.  = 

550         x 

number  of  horse-powers,  62  '5  =  weight  of  a  cubic  foot  of 
water,  550  =  number  of  pounds  in  one  second  by  one 
horse-power,  x  =  per  cent  of  efficiency,  V  =  volume  of 
air  delivered  in  cubic  feet  per  second,  h  =  the  relative 


AIR-PROPELLERS. 


87 


weight  of  the  air  compared  with  an  equal  bulk  of  water. 
As  the  air  is  denser  than  normal  when  being  forced 
through  the  ducts,  h  must  be  determined  by  the  ma- 
nometer. V  can  be  found  by  means  of  an  anemometer. 
(See  Appendix  C.) 

Combs' s  Fan  is  of  different  construction,  but  as  its 
per  cent  of  efficiency  is  somewhat  less  than  that  of  Kit- 
tenger's  it  will  not  here  be  discussed. 

Fm.  13. 


88     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

Blackmaris  Fan  (see  Fig.  13). — As  an  example  of  mod- 
ern improvement  in  revolving  fans,  I  copy  from  the 
patent-office  specifications  the  description  of  what  seems 
to  me  one  of  the  best  yet  constructed  (see  Appendix  F). 

TJie  Hope  Fan. — An  improvement  on  the  Blackmail 
Fan  has  recently  (1886)  been  patented  by  Hope  Brothers, 
of  Kansas  City,  Missouri.  The  improvement  consists  of 
a  slight  modification  of  the  vanes,  and  the  conversion  of 
the  whole  fan  into  a  water  motor,  which  is  the  power 
used. 

This  fan  motor  undoubtedly  possesses  some  advan- 
tages over  any  other  yet  devised.  It  can  be  used  either 
as  an  exhauster  or  a  perflator,  and,  by  being  placed  di- 
rectly at  the  entrance  into  the  room,  the  loss  from  fric- 
tion of  moving  air  through  long  ducts  is  prevented.  By 
applying  the  power  at  the  circumference  of  the  wheel, 
instead  of  near  the  center,  as  is  usual  when  belting  from 
an  engine,  much  power  is  gained,  especially  when  a  rela- 
tively small  quantity  of  water  is  used  under  high  pressure. 

Of  course,  when  other  things  are  equal,  no  gain  would 
be  realized  by  applying  the  power  at  the  circumference, 
as  what  is  thus  gained  in  power  would  be  lost  in  velocity, 
but  in  the  case  supposed,  where  a  small  stream  of  water 
under  high  velocity  is  used,  much  of  the  effective  power 
will  exist  in  its  vis  viva  as  it  strikes  the  buckets.  Now, 
as  the  vis  viva  is  proportional  to  the  mass  of  the  moving 
body,  and  to  the  square  of  its  velocity,  the  increase  of 
velocity  will  be  more  effective  than  an  increase  of  mass. 

One  of  these  fans  is  adequate  to  move  the  air  of  a 
school-room  of  ordinary  size.  It  can  be  run  for  five  cents 
per  hour,  as  proved  by  actual  experiment  in  Kansas  City, 
when  the  water  pressure  is  eighty  pounds. 

Patent  of  Hendry  and  Others. — One  of  the  most  ad- 
vantageous arrangements  is  to  put  the  fan  in  the  angle  of 


AIR-PROPELLERS. 


89 


the  shaft  and  ventilating  duct,  as  illustrated  in  Fig.  14. 
The  advantage  gained  in  this  arrangement  consists  in  car- 


FIG.  14. 


B 


rying  the  entering  air  only  one  fourth  of  a  revolution  be- 
fore releasing  it. 

In  the  figure,  the  arrows  show  the  direction  of  the 
fan's  revolution,  and  also  the  direction  taken  by  the  air. 
As  the  vane  a  is  moving  forward  in  its  present  position  it 
carries  in  front  of  it  the  air  in  the  lower  part  of  the  shaft 
A ;  the  tangential  motion  which  the  revolution  gives  to 
this  air  will,  when  one  fourth  of  a  revolution  has  been 
made,  send  it  through  the  duct  B.  This  manner  of  plac- 
ing the  fan  is  used  by  A.  J.  Ilendry,  of  Georgia,  in  an 
invention  patented  in  1883.  The  amount  of  friction 


90     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

which  this  arrangement  obviates  would  allow  the  use  of 
clock  motors  which  could  be  wound  up  at  stated  inter- 
vals. A  shaft  and  tube  could  be  supplied  each  room,  and 
the  motors  thus  distributed  would  furnish  ample  power 
for  propulsion. 

The  plenum  movement,  so  far  as  at  present  attained 
in  practice,  will  deliver  from  fifty  to  one  hundred  and 
fifty  cubic  feet  of  air  per  horse-power  per  second.  But 
these  estimates  have  been  made  irrespective  of  accompa- 
nying effects  of  natural  ventilation.  In  arranging  for  the 
plenum  movement  every  provision  should  also  be  made  to 
derive  all  possible  aid  from  natural  movement.  When- 
ever it  is  possible  to  ventilate  by  natural  means,  the  me- 
chanical means  could  be  suspended.  It  should  be  the 
object  of  the  plenum  movement  to  supplement  the  natu- 
ral, not  to  replace  it.  By  working  with  Nature  as  an  aid 
the  amount  of  power  required  would  be  greatly  lessened. 


CHAPTER  XIV. 

CAN  THE   PLENUM   MOVEMENT   BE  AFFORDED  ? 

IN  order  to  answer  this  question  understand ingly  it 
will  be  necessary  to  enter  into  somewhat  lengthy  detail 
concerning  the  amount  of  heat  needed,  the  amount  of 
unavoidable  waste,  and  the  amount  of  fuel  necessary  to 
the  supply  ;  then  to  consider  the  cost  of  adding  thereto 
the  cost  of  the  plenum  movement,  and  to  compare  the 
total  estimate  thus  made  with  present  expenditures. 

In  making  these  estimates  I  shall  consider  a  single 
room,  of  average  size,  and  supposing  the  average  conditions 
as  to  exposure,  number  of  windows,  locality,  etc.  The 


CAN  THE  PLENUM  MOVEMENT  BE  AFFORDED?        91 


Maximum  number  of 
degree*  tempera- 
tmre  to  be  raised. 


Average  number  of 
degrees  tempera- 
ture to  be  raited. 


Mean  temperature  of  | 
fire  months. 


No.  of  montiu  fir 
required. 


i        i 


i  i   T    i 


T-T-          <- 


* 


1-  oo  oo  i-  o  co  oo  i>  i>  t* 


g 


>.;Mean. 

*     


nssggssssgsgg  §sgsssss 


«  »« 


•3  •  -t>o 


£2     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

table  on  page  91  shows  the  minimum  and  mean  tempera- 
tures of  each  month,  compiled  from  observations  of  the 
Signal  Service,  U.  S.  A.,  and  Blodgett's  "Climatology  of 
the  United  States."  As  the  table  shows,  the  amount  of 
heat  required  depends  partly  on  the  latitude  and  locality 
of  the  place.  I  select  for  our  estimate  that  of  Chicago,  as 
representing  a  high  average,  but,  of  course,  at  places  far 
north  or  south,  other  figures  will  be  found  in  the  table 
which  will  be  more  appropriate.  70°  is  taken  as  the  tem- 
perature of  comfort,  and  to  which  existing  temperature 
must  be  raised.  Taking  seven  as  the  number  of  months 
fire  is  required  ;  the  average  temperature  of  these  months 
35°  ;  then  the  average  number  of  degrees  of  temperature 
to  be  raised  will  be  70°  —  35°  =  35°.  Taking  the  average 
number  of  pupils  in  one  room  as  60,  the  cubic  feet  of  air 
required  in  one  hour  will  be  60  X  3,000  =  180,000.  A 
thermal  unit,  or  unit  of  heat,  is  the  amount  of  heat  re- 
quired to  raise  one  pound  of  water  one  degree.  By  careful 
experiment  and  comparison  of  the  specific  heats  of  air  and 
water,  it  is  established  that  this  amount  of  heat  —  one 
thermal  unit — will  raise  48  cubic  feet  of  air  one  degree. 

180,000 

Then  — ^ —  =  3,750  =  number  of  thermal  units  neces- 
sary to  raise  180,000  cubic  feet  of  air  one  degree,  and 
3,750  X  35,  the  average  number  of  degrees  to  be  raised, 
equal  131,250,  the  number  of  thermal  units  necessary  to 
supply  the  occupants  of  one  school-room  one  hour. 

Loss  through  the  Walls. — The  formulas  which  it  will 
be  necessary  to  use  in  making  these  estimates  may  seem 
difficult,  but  they  have  been  deduced  from  well-known 
laws  and  properties  of  matter  familiar  to  every  physicist, 
and  formulated  by  the  best  European  mathematicians. 
They  are  in  practical  use  by  skilled  engineers  everywhere. 
The  loss  of  heat  through  walls,  when  all  sides  of  the  build- 


CAN  THE  PLENUM   MOVEMENT   BE   AFFORDED?        93 

ing  are  exposed,  may  be  calculated  from  the  formula  U  = 

,  *     ,   . : — ~.  where  U=  total  units  of  heat  lost  per 

C  (2  l*+r)+el-tq 

hour  per  square  foot ;  I*  —  loss  by  contact  of  air  for  a 
difference  of  1°  =  '4912  when  the  air  is  moving ;  C  =  con- 
ducting power  of  material  (see  table,  Appendix  D,  page 
167);  r  =  radiating  power  of  material  (see  table,  Appendix 
E,  page  168) ;  q  =  r  +  It ;  T  =  temperature  of  air  in  the 
room  ;  T,  =  temperature  of  external  air  ;  e  =  thickness  of 
wall  in  inches.  The  loss  of  heat  through  floors  and  ceilings 
when  not  exposed  to  the  external  air  is  usually  regarded 
as  null.  Taking  26  feet  X  34  X  14  as  the  size  of  the 
average  school-room,  120  X  14  =  1680,  area  of  walls  in 
square  feet.  Counting  six  windows,  each  9  X  3£  feet, 
9  X  3£  X  6  =  188,  area  of  windows  ;  1680  —  188  =  1492 
square  feet  of  wall  surface.  The  wall  is  supposed  to  be 
18  inches  thick. 

The  values  in  this  example  to  be  used  in  the  above 
formula  will  be  I,  =  -4912  ;  c  =  4-83  ;  q  =  r  +  I,  =  -7358 
+  -4912  =  1-227  ;  r  =  '7358  ;  e  =  18  inches  ;  T  =  70°  ; 
T,  =  35°.  Then 

n -4912X4 -83  XI '227X35  _101-88__ 

~4-83  (2X4-912+ -7358)+18x4-912xl-227~  19-13  ~ 
5-32  =  thermal  units  per  square  foot  per  hour;  5 -32  X 
1492  =  7937-44  =  thermal  units  lost  through  the  walls  in 
one  hour. 

Loss  through  Windows. — "When  the  windows  are  not 
more  than  £  inch  in  thickness  the  following  formula  is 
used  for  finding  the  value  of  U  :  U  =  q  (T  —  (4),  where 
tt  —  temperature  of  the  glass  ;  q  =  r  -\-  It ;  r  =  radiating 
power  of  the  glass  ;  h  =  loss  by  contact  of  air  for  a  differ- 
ence of  1°  =  -4912. 

The  values  in  this  example  are,  q  =  (r  +  It)  =  (-5948 
+  -4912)  =  1-086,  T  =  70°  ;  tt  =  *f-=  17*5  J  then  U  = 


94     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

1*086  X  17*5  =  19  =  thermal  units  per  square  foot. 
Area  of  six  windows  =  188  square  feet  X  19  =  3572  = 
loss  through  the  windows  in  one  hour. 

Total  Loss. 

From  incoming  fresh  air  ............  131,250 

From  walls  ......  ...................       7,937 

From  windows  ......................       3,572 

Total  thermal  units  ............  142,759 

Now,  in  the  burning  of  one  pound  of  coal  13,000  ther- 
mal units  are  evolved.  The  efficiency  of  a  heating  appa- 
ratus depends  upon  the  amount  of  surface  exposed  and 
skill  in  firing.  In  practice,  the  efficiency  of  heaters  is 
from  38  per  cent  to  80  per  cent  of  the  whole  heat  evolved. 
Taking  60  per  cent  as  a  fair  average  of  efficiency, 

142,759       100 

'  X  -777-  =  18'3-J-,  number  of  pounds  of  coal  re- 
lo,000  oO 

quired  for  one  room  for  one  hour.     From  this  as  a  unit  the 

cost  for  a  building  of  any  number  of  rooms  may  be  obtained. 

For    example,  counting    seven    the   number  of  fire 

months,  eight  as  the  number  of  hours  per  day  in  which 

fire  will  be  needed,  $5  the  price  of  a  ton  of  coal,  the  cost 

of  heating  a  building  of  ten  rooms  would  be, 

18-3  X  20  X  7X  8  X  5X  10 


2000 

Now,  under  the  conditions  supposed,  this  will  be  the 
necessary  expense  ;  any  less  would  imply  that  the  chil- 
dren and  teachers  are  fed  on  impure  air.  To  heat  such 
vast  quantities  of  air  as  the  conditions  of  sufficient  venti- 
lation necessitates  requires  large  expenditures  of  heat. 
There  is  no  help  for  this.  The  rations  of  pure,  life- 
giving  air  measured  out  to  children  shut  up  in  close 
houses  should  be  as  certain  a  quantity  as  the  daily  allow- 
ance of  bread  and  butter. 


CAN   THE  PLENUM   MOVEMENT   BE  AFFORDED?        95 

By  examining  reports  of  school  boards  from  various 
cities  I  find  that  the  expenditure  above  calculated  is 
not  far  from  the  actual  average  cost  of  supplying  such 
school-houses  similarly  conditioned.  That  is  to  say,  the 
present  expenditure  for  fuel  is  sufficient  to  supply  the 
most  rigid  demands  of  sanitary  ventilation. 

"We  are  not  ready,  however,  to  conclude  that  all  is 
well.  The  coincidence  of  these  facts  proves  nothing. 
There  would  have  to  be  an  important  additional  element 
to  make  these  two  first  facts  possess  a  causal  relation  to 
each  other.  If  the  school  expending  this  amount  of  fuel 
should  be  visited  by  an  expert  who,  after  examining  the 
air,  testing  for  C0«  and  noting  the  rate  of  renewal,  found 
that  the  air  was  being  renewed  every  six  to  seven  minutes, 
and  the  CO*  not  above  *2  per  1000  of  air,  then  the  con- 
clusion would  follow  that  the  expenditures  had  been  made 
economically. 

But,  unfortunately,  this  important  third  element  is 
wanting.  The  real  facts  are  too  well  known  to  admit  of 
any  mistake  here.  Instead  of  the  air  of  the  average 
school-room  being  changed  every  six  minutes,  it  is  not 
changed  oftener  than  once  in  thirty  minutes,  and  more 
frequently  probably  not  oftener  than  once  per  hour.  In 
thousands  of  houses  it  is  not  changed  at  all,  just  enough 
air  working  its  way  in  by  diffusion  to  prevent  immediate 
death  by  suffocation. 

These  are  the  facts.  It  would  be  tedious  to  enumer- 
ate the  commissions  which  have  from  time  to  time  in  dif- 
ferent parts  of  the  world  been  appointed  to  investigate 
this  subject.  Whjle  there  is  variety  in  the  character, 
number,  and  locality  of  these  investigations,  there  is 
singular  unanimity  of  results.  The  invariable  verdict 
of  all  may  be  epitomized  as  bad,  BAD,  BAD  !  Some  are 
better  than  others  (or,  rather,  some  are  not  so  bad  as 
10 


96     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

others),  but  the  difference  is  rather  in  degree  than  in 
kind. 

The  question  which  now  confronts  us  is,  What  became 
of  the  heat  from  all  of  that  coal  ?  There  is  but  one  an- 
swer :  It  was  wasted.  There  may  be  many  sources  for 
this  waste.  Windows  and  doors  are  thrown  open  to  re- 
lieve the  temporary  inconvenience  of  a  depressing  atmos- 
phere. These  openings,  especially  when  near  the  heater 
or  incoming  warm  air,  at  once  become  outlets,  setting 
the  current  toward  them,  and  drawing  out  the  warm, 
pure  air  as  fast  as  furnished. 

Too  small  heating  surfaces  or  unskillful  firing  may 
also  be  causes  of  waste.  Overheating  the  air  and  con- 
fining in  the  top  of  the  room  (as  is  the  practice  of  some 
hot-air  systems)  till  it  cools  down  to  the  temperature  of 
comfort  is  a  positive  waste  by  conduction  through  the 
upper  walls  and  windows.  .  The  only  way  to  utilize  the 
excess  of  heat  in  supra-heated  air  would  be  to  thoroughly 
mix  it  with  such  an  amount  of  cold  air  as  would  be  re- 
quired to  reduce  the  temperature  to  that  of  comfort. 

In  view  of  this  state  of  the  case,  what  is  the  remedy  ? 
How  is  the  heat  which  is  being  expended  to  be  utilized  ? 
The  answer  is  evident.  There  must  be  some  means 
whereby  the  air  in  a  room  may  be  changed  with  requisite 
frequency,  and  this  independent  of  the  doors  and  win- 
dows. The  heating  surface  must  be  properly  propor- 
tioned to  the  amount  of  fuel  consumed  in  order  to  lessen 
the  waste  through  the  smoke  chimney.  Air  must  not  be 
heated  much  above  the  temperature  at  which  it  is  to  be 
used,'  in  order  that  there  may  not  be  loss  in  cooling. 

We  return  now  to  the  original  question,  Can  the 
plenum  movement  be  afforded  ?  Can  the  extra  expense 
of  moving  this  air  through  the  building  be  assumed  by 
the  people  ?  This,  it  seems  to  me,  is  much  like  the 


THE  COST  OF  VENTILATION.  97 

question  of  a  man  who,  after  having  paid  a  high  price  for  a 
stove,  asked  his  wife  if  they  could  afford  the  coal  to  build 
a  fire  in  it.  Not  to  provide  the  means  of  utilizing  ex- 
pense already  incurred  is  simply  to  waste  this  expense. 

I  am  aware  that  many  economize  by  an  exact  count 
of  dollars  and  cents  concerned  in  immediate  expenditures. 
But  to  this  question  true  economy  has  but  one  answer  : 
TJiis  air  must  in  some  way  be  moved.  If  it  can  be  done 
by  aspirating  chimneys,  of  proper  size  and  construction, 
very  well ;  if  not,  it  must  be  moved  by  mechanical  means. 
At  all  events,  it  must  be  moved  by  some  means. 


CHAPTER  XV. 

THE  COST  OF  VENTILATION. 

Cost  of  the  Aspirating  Chimney. — Let  us  approximate 
the  cost  first  of  the  aspirating  chimney.  We  have  seen 
(see  Appendix  B)  that  where  the  fresh-air  inlets  are  of 
adequate  area  the  velocity  of  the  air  in  the  ducts  should 
be  at  least  7*7  feet  per  second,  say  8  feet.  Assume  the 
height  of  the  aspirating  chimney  to  be  70  feet. 

To  find  the  sectional  area  of  an  aspirating  chimney 
which  is  to  take  away  all  the  air  that  passes  in  one  hour, 

V 

we  have  A  =  ...  ...    ,  where  A  =  the  sectional  area  of  the 

00,000  v 

aspirating  chimney ;  V  =  volume  of  air  passing  through 
the  chimney  per  hour  ;  v  =  velocity  of  air  per  second  in 
ducts  ;  3,600  =  seconds  in  one  hour.  Then  the  sectional 
area  of  a  chimney  required  for  a  single  room  in  our  exam- 

.     ,        .  180,000 

plo  above  is  A  =  -— -f-  --  =  6 -2  square  feet.      The  ve- 


98     VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

locity  of  the  air  will  depend  upon  the  difference  of  tem- 
perature between  the  air  in  the  chimney  and  the  air 
outside. 

Now,  the  number  of  degrees  temperature  which  the 
air  in  the  chimney  will  have  to  be  raised  in  order  to 
produce  a  velocity  of  8  feet  (or  other  given  rate)  may 

v*(l+et}(l+fl-+f\ 

be  formulated  :  /„  = '  -  ft  -  t), 

2gh 

where  ts  =  increase  of  temperature  by  fire  ;  v  =  velocity 
of  air  in  feet  per  second  in  ducts  ;  e  =  expansion  of  air 
per  1°  temperature  =  '00203  ;  t  =  external  temperature  ; 
f=  co-efficient  of  friction  in  ducts  ;  1=  total  length  of 
ducts  ;  d  =  diameter  of  ducts  ;  U  =  internal  temperature 
of  room  ;  g  =  accelerated  gravity  ;  h  =  height  of  chim- 
ney ;  /i  =  co-efficient  of  friction  in  elbows. 

The  corresponding  values  in  our  example  are  :  v*  — 
8'  =  64  ;  e=  '00203  ;  t  =  35°  ;  /  =  -05  (for  rough  flues)  ; 
fi  =  4'5  (assuming  three  square  elbows,  which  is  proba- 
bly a  fair  average) ;  I  =  180  (this  includes  the  height  of 
the  chimney,  the  height  of  the  pure-air  shaft,  and  the 
ducts) ;  180  is  a  fair  average  ;  d  =  2  '5  (for  estimate  made 
on  necessary  size  of  total  inlets,  q.  v.) ;  g  =  32 '16  ;  h  = 
70  feet ;  ti  =  70°.  Substituting  these  values  : 

64  (1  +  -00203  X  35)  ( 1  +  -05  ~^-  +  4's) 

/  _ l_         J~-Z—J  —  35  = 

2  X  32-16  X  70  X  '00203 

- 
"' 


The  quantity  of  coal  necessary  to  produce  any  given 

/  s  W 
temperature  is  -expressed  K  =  -— r- ,  where  K  =  number 

of  pounds  of  coal  per  hour  ;  s  =  specific  heat  of  air  = 
•238  ;  W  =  weight  of  air  in  pounds  carried  off  per  hour  ; 


THE   COST  OF  VENTILATION.  99 

u  =  units  of  heat  utilized  in  one  pound  of  coal  when 
burned  on  a  grate  =  6000  ;  %  =  per  cent  of  loss  by  radia- 
tion through  wall  of  chimney  =  '9. 

Present  values.:  tt  =  33-35°  ;  a  =  '238  ;  W  =  14,400 
pounds  (weight  of  1  cubic  foot  of  air  at  35°  being  -08,  then 
180,000  X  '08  =  14,400)  ;  %  =  -9.  Substituting  :  K  = 

33-35°  X  '238  X  14,400  0,  ,  ,  ,  . 
— -r— r =  21,  the  number  of  pounds  of 

Oj^rUly 

coal  necessary  to  burn  per  hour  on  a  grate  in  the  chimney 
in  order  to  secure  sufficient  ventilation. 

This,  it  will  be  observed,  is  more  by  nearly  3  pounds 
per  hour  than  was  found  to  be  required  for  heating. 
Evidently,  then,  coal  burned  on  a  grate  in  an  aspirating 
chimney,  for  the  purpose  of  creating  a  draft,  is  expensive. 
Can  it  be  afforded  ?  If  there  were  no  better  way  to  ac- 
complish the  same  work  there  would  be  bat  one  answer  : 
Yes,  of  course,  it  can  be  afforded,  for  the  children  and 
teachers  must  have  air. 

But  this  supposed  expense  is  not  necessary.  Instead 
of  heating  the  aspirating  chimney,  as  heretofore  described, 
it  may  be  combined  with  the  smoke  chimney,  which  will 
generally,  if  properly  constructed,  be  sufficient  to  heat 
the  aspirating  chimney  to  the  required  degree.  This 
may  be  done,  has  been  done,  in  various  ways.  The  foul- 
air  ducts  may  lead  to  an  aspirating  chimney  built  around 
the  smoke  chimney  so  as  to  be  warmed  by  it.  They  may 
open  directly  into  the  smoke  chimney,  either  above  or 
below  the  fire,  or  they  may  be  carried  up  to  near  the  top 
before  entering.  On  account  of  a  possible  tendency  to 
smoke  in  windy  weather,  it  is  probably  best  to  have  the 
chimneys  so  arranged  that  the  heat  from  the  smoke  chim- 
ney may  be  utilized  in  the  aspirating  chimney  without 
direct  communication  between  them  internally.  To  effect 
this,  I  would  suggest  that  the  smoke  and  escaping  heat 


100  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


from  the  heater  be  carried  off  through  a  large  number  of 
small  metallic  tubes  extending  up  through  the  chimney. 
The  large  surface  thus  exposed  to  the  air  inside  the  chim- 
ney would  thoroughly  heat  it  to  the  temperature  required 
in  an  aspirating  chimney. 

In  Fig.  15,  C  represents  the  wall  of  the  chimney ;  F, 
the  furnace  ;  the  lower  arrows,  the  course  through  the 

FIG.  15. 


tubes  taken  by  the  smoke  ;  D,  the  foul-air  duct  leading 
from  the  school-room ;  the  upper  arrows,  the  course  be- 
tween the  tubes  taken  by  the  foul  air.  A  number  of 
small-sized  stove-pipes  would  answer  well  for  the  tubes. 
In  this  case  the  chimney  would  have  to  be  made  large 
enough,  so  that  a  cross-section  of  the  chimney,  minus  the 
sum  of  the  cross-sections  of  the  tubes,  would  leave  a 


THE  COST  OF  VENTILATION.  101 

remainder  equal  to  the  required  size  of  aii  aspirating 
chimney. 

The  main  trouble  with  aspirating  chimneys  has  been 
from  making  them  entirely  too  small.  We  saw  above 
that  the  sectional  area  necessary  for  a  single  school-room 
is  over  6  square  feet.  Calling  it  6,  then,  for  six  rooms, 
it  would  be  36  square  feet — 6  feet  square.  For  eight 
rooms,  48  square  feet — nearly  7  feet  square.  For  four- 
teen rooms,  84  square  feet — over  9  feet  square.  In  the 
arrangement  above  illustrated  the  necessary  area  for 
smoke-flues  must  be  added  to  these  numbers  to  obtain 
the  size  which  the  chimney  would  have  to  be  built. 

To  calculate  the  area  of  smoke-flues,  engineers  usually 

jr 

use  the  formula  A  =  *128 — — .  where  A  =  sectional  area 

Vh 

in  square  feet ;  K  =  pounds  of  coal  consumed  in  one 

hour  ;  *128  =  a  constant ;  h  =  height  of  chimney  in  feet. 

The  corresponding  values  in  the  present  calculation 

•I  0.0 

are  :  K  =  18-3  ;  h  =  70.      Then  A  =  -128  ^~  =  -279 

V70 

square  feet  =  '279  X  144  =  40-1  square  inches.  We  found 
above  that  the  necessary  area  of  an  aspirating  chimney 
for  one  room  is  6  '2  square  feet  =  892  '8  square  inches  ; 
40 '1  inches  being  '044  of  892 '8  square  inches,  the  en- 
tire size  of  the  chimney,  including  smoke-  and  foul-air 
flues,  may  be  found  by  multiplying  the  necessary  aspirat- 
ing chimney  area  by  1'044.  Then  6*2  square  feet,  the 
area  of  an  aspirating  chimney  for  one  room,  multiplied 
by  1'044  =  6 '472  square  feet.  This  is  sufficient  to  show 
that  the  chimneys,  when  intended  for  the  double  purpose 
of  carrying  smoke  and  foul  air,  must  be  large  and  high. 
On  this  account,  where  there  are  more  than  six  rooms  in 
the  same  building,  it  is  better  to  have  two  chimneys.  It 


102  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

thus  appears  from  the  foregoing  that,  by  a  properly-con- 
structed aspirating  chimney,  ventilation  may  be,  under 
favorable  conditions,  secured  without  additional  cost  for 
fuel.  The  attendant  unfavorable  conditions  will  be  no- 
ticed presently. 

Cost  of  the  Plenum  Movement. — Now,  to  calculate  the 
cost  of  the  plenum  movement :  If  the  Eittenger  fan  be 
used,  and  calling  its  per  cent  of  efficiency  40 — the  value 
of  x  in  formula  for  estimating  Hp.  (see  page  86) — we 
have  Hp.  =  '28  V  h  (h  =  height  of  manometer).  In  the 
present  example  V  =  180,000  ;  h  =  *08  (taking  the  av- 

\      rru      TJ          -28  X 180, 000  X '08 
erage).     Then  Hp.  = =  1-1,  say  one 

horse-power  for  each  room.  In  practice,  it  requires  from 
5  to  8  pounds  of  coal  per  horse-power  per  hour,  so  that 
the  cost  of  moving  the  air  by  mechanical  power  would  be 
about  one  third  of  the  cost  of  heating. 

This  estimate  is  made  without  reference  to  recent  im- 
provements which  have  been  made  in  fans  and  blowers 
for  moving  air  more  economically.  The  efficiency  of  the 
Blackman  fan  is  doubtless  as  much  as  70  per  cent,  and, 
with  the  Hope  water-motor  fan,  where  the  water-pressure 
is  as  much  as  60  pounds  to  the  square  inch,  the  cost  would 
not  be  more  than  one  third  of  that  of  the  one  above  cal- 
culated. 

It  is  also  important  to  remember  that,  in  this  calcula- 
tion, enough  power  has  been  provided  to  remove  the  air 
independent  of  the  aid  of  aspirating  chimneys.  The  as- 
pirating chimney  should  be  considered  one  of  the  essential 
parts  of  every  school-house.  It  will  cost  nothing  but  the 
first  cost  of  building,  except  in  warm  weather,  when  heat- 
ing is  not  necessary  ;  when,  of  course,  means  must  be 
provided  to  build  a  fire  in  it  for  the  sole  purpose  of  cre- 
ating a  draft.  The  aspirating  chimney  always  serves  a 


THE  COST  OF  VENTILATION.  103 

good  purpose,  and,  in  ordinary  conditions,  will  be  suffi- 
cient for  all  the  purposes  of  ventilation  ;  but  there  will 
be  times  when  it  will  not  be  wholly  adequate.  In  windy 
weather  it  is  impossible  so  to  regulate  the  draft  that  all 
the  rooms  of  a  large  building  will  be  ventilated  equally. 

Again,  it  must  not  be  forgotten  that  the  aspirating 
chimney,  drawing  as  it  does  the  air  from  the  room,  is  a 
vacuum-forming  process,  so  that  the  incidental  openings 
of  doors  and  windows,  as  well  as  the  crevices  around  im- 
perfect fitting  ones,  necessarily  become  inlets,  thus  inter- 
fering with  the  draft  through  the  inlets  intended  to  admit 
the  fresh  warm  air.  (Let  it  be  repeated  and  emphasized 
here,  that  in  cold  climates  double  windows  should  be  pro- 
vided. They  lessen  by  one  half  the  amount  of  heat  lost 
by  conduction  through  them,  as  well  as  shut  off  air-cur- 
rents where  they  are  not  wanted.) 

It  becomes  evident,  then,  that  in  systems  now  in  use 
the  plenum  movement  is  necessary  as  a  supplement  to  the 
aspirating  chimney.  This  gives  a  fullness  of  air  in  the 
room,  restoring  the  balance  between  internal  and  external 
air,  made  unequal  by  the  aspirating  chimney  when  acting 
alone.  It  also  establishes  the  current  independent  of  ac- 
cidental openings,  and  prevents  interference  to  draft  in 
windy  weather.  When  thus  working  with  the  chimney, 
the  power  required  is  of  course  much  less  than  when 
alone  doing  the  whole  work  of  moving  the  air.  It  should 
be  under  the  control  of  a  competent  janitor,  who  could 
regulate  its  working  to  suit  existing  conditions. 

Considering,  then,  the  plenum  movement  as  a  supple- 
mentary aid,  taking  advantage  of  modern  improvements 
in  propellers,  and  supposing  the  adjustments  to  be  super- 
vised by  one  who  understands  the  principles  of  ventila- 
tion, there  remains  no  room  for  doubt  as  to  whether  this 
method  of  ventilation  can  be  afforded.  It  not  only  can 


104  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

be  afforded,  but  it  should  be  regarded  as  indispensable. 
Nothing  is  more  needed  in  this  age  than  a  general  en- 
lightenment on  this  subject  of  ventilation.  Ignorance  of 
employes  should  be  no  excuse  for  deferring  necessary 
improvements.  The  improvements  are  needed  by  the 
public.  The  public  are  willing  to  pay  for  them,  and 
there  are  persons  competent  to  make  them.  When  this 
kind  of  service  is  demanded,  the  supply  will  follow  as 
a  natural  consequence. 


CHAPTER  XVI. 

WARMING. 

Heat :  The  Amount  needed  for  Comfort. — The  degree 
of  temperature  most  conducive  to  health  is  not  a  con- 
stant. The  temperature  varies  not  only  for  different  in- 
dividuals but  for  the  same  individuals  at  different  times. 
A  youthful,  healthy  adult,  actively  employed,  will  be 
comfortable  at  a  temperature  of  60°,  while  elderly  persons 
or  invalids  require  a  temperature  of  68°  to  75°.  Children 
generally  require  a  higher  temperature  than  adults,  and 
this  especially  when  they  are  bodily  inactive,  as  in  the 
school-room.  It  is  impossible  to  fix  the  temperature  of  a 
school-room  to  suit  the  changing  conditions  and  indi- 
vidual characteristics  of  all,  but  some  degree  must  be 
maintained  which  most  nearly  approximates  the  average 
necessities.  A  temperature  of  70°  is  generally  considered 
the  proper  degree  for  school-rooms  ;  it  is  probably  as 
nearly  correct  as  any  fixed  temperature  can  be. 

The  relative  humidity  of  the  air  has  something  to  do 
with  the  temperature  which  will  be  most  conducive  to 


WARMING.  105 

comfort.  In  a  moist  atmosphere  a  temperature  of  65° 
would  probably  seem  as  warm  as  70°  in  a  dry  atmosphere. 
It  is  worthy  of  remark  here  that  many  medical  authorities 
think  that  the  American  tendency  is  to  overheat  our 
houses,  and  that  a  much  lower  temperature  than  that 
generally  maintained  would  be  more  healthy.  Feeling  is, 
no  doubt,  the  truest  guide  to  the  proper  temperature. 
The  body  should  be  made  comfortable,  even  if  a  higher 
temperature  be  required  than  is  thought  normal.  If  an 
individual's  circulation  is  so  sluggish  as  to  require  a  high 
temperature  to  maintain  comfort,  the  remedy  is  not  in 
an  immediate  deprivation  of  the  heat,  but  in  removing 
the  desire  for  it  by  exercise  and  due  attention  to  the  laws 
of  health. 

The  Transmission  of  Heat. — Heat  is  transmitted  in 
three  ways — by  conduction,  by  radiation,  and  by  convec- 
tion. By  conduction,  heat  passes  through  bodies  from 
particle  to  particle,  without  any  change  of  relative  posi- 
tion between  the  particles.  Heat  applied  to  one  end  of  a 
metallic  rod  passes  through  its  entire  length.  The  facility 
with  which  heat  passes  by  conduction  depends  upon  the 
nature  of  the  medium  through  which  it  passes.  All  sub- 
stances conduct  heat,  but  some  so  slowly  that  they  are 
sometimes  called  non-conductors.  In  general,  the  metals 
are  good  conductors,  while  air,  water,  and  dry  vegetable 
fabrics,  such  as  wood,  cotton,  etc.,  are  bad  conductors. 

The  conductivity  of  bodies  usually  diminishes  as  the 
temperature  is  raised,  though  no  definite  laws  of  the  rate 
of  this  decrease  have  been  formulated.  This  fact  becomes 
important  in  house-heating,  and  furnishes  another  objec- 
tion to  overheating  stoves  and  heaters  ;  for  while  in  this 
condition  they  not  only  become  pervious  to  poisonous 
gases,  but  by  their  diminished  conductivity  compel  the 
heat  to  seek  an  exit  through  the  chimney  instead,  of  con- 


106  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

ducting  it  into  the  room.  In  selecting  stoves  and  heat- 
ers, due  precaution  should  be  exercised  on  these  two  im- 
portant points,  thus  securing  a  maximum  of  heat,  and  a 
minimum  of  escaping  gases.  Heaters  should  therefore 
be  large,  so  as  to  furnish  a  large  surface  moderately 
heated,  instead  of  a  small  surface  highly  heated.  They 
should  be  lined  with  fire-clay  or  brick,  to  intercept  the 
poisonous  carbonic  oxide  and  other  gases.  By  the  con- 
ductivity of  iron  the  heat  stored  up  in  steam  or  hot  water 
is  utilized  in  a  room  after  having  been  carried  some  dis- 
tance from  the  source  of  the  heat.  It  will  also  be  a 
source  of  great  waste  if  the  convey-pipes  leading  to  the 
several  places  where  heat  is  wanted  are  not  packed  in 
some  non-conducting  material,  to  prevent  the  escape  of 
heat  into  places  where  it  is  not  wanted. 

Radiation. — Eadiant  heat  differs  from  conducted  heat 
in  several  ways.  While  conducted  heat  requires  a  sensi- 
ble medium  for  its  transmission,  and  a  time  which  is  de- 
termined by  the  nature  of  that  medium,  radiant  heat  re- 
quires no  such  medium,  and  travels  with  the  velocity  of 
light.  Eadiant  heat  will  perhaps  be  better  understood  by 
a  few  introductory  remarks  on  light,  with  which  radiant 
heat  is  probably  identical.  Without  entering  into  a  dis- 
cussion of  radiant  energy,  it  may  be  said  that  all  experi- 
mental observation  thus  far  serves  to  corroborate  the 
theory  that  light  is  a  mode  of  molecular  motion  in  a  sub- 
tile medium  not  cognizable  to  the  senses  and  permeating 
all  space.  It  travels  at  the  rate  of  185,000  miles  per  sec- 
ond. Its  effects  on  life  are  well  known,  it  being  the 
prime  active  agent  in  all  vegetable  and  animal  existence. 
If  a  beam  of  solar  light  be  admitted  into  a  darkened  room 
and  allowed  to  pass  through  a  prism,  it  divides  into  seven 
parts,  and,  if  projected  on  a  white  wall  or  screen,  it  will 
appear  in  as  many  different  colors,  red,  orange,  yellow, 


WARMING.  107 

green,  blue,  indigo,  and  violet,  commonly  called  the  solar 
spectrum.  When  passing  from  one  medium  to  another 
of  different  density  light  is  bent  out  of  its  direct  course. 
This  is  termed  refraction.  Now,  in  the  solar  spectrum 
the  several  parts  denoted  by  the  seven  colors  are  refracted 
at  different  angles,  the  red  least  and  the  violet  most.  It 
is  this  which  makes  the  light  spread  out  like  a  fan  and 
appear  as  a  continuous  band  on  the  screen. 

These  colors,  when  examined  separately,  manifest 
properties  somewhat  different,  though  they  have  many 
properties  in  common.  The  red  ray — the  least  refracted 
— shows  the  greatest  heat,  and  the  violet  the  least.  By 
Xewton's  interference  disks  it  is  proved  that  these  rays 
also  differ  in  wave-length,  the  red  being  the  longest  and 
the  violet  shortest,  but  their  vibratory  rapidity  is  in- 
versely as  their  length.  In  common,  all  these  rays  have 
the  property  of  reflection,  refraction,  and  polarization. 
The  relevancy  of  these  remarks  will  now  appear. 

If  the  spectrum  be  examined,  just  beyond  the  red, 
where  it  appears  dark,  it  will  be  found  to  possess  the  same 
characteristics,  except  visibility,  as  other  parts  of  the 
spectrum.  The  ratio  of  increasing  heat  from  the  violet 
to  the  red  is  continued  into  the  dark  part,  which  is  found 
to  be  of  a  higher  temperature  than  any  other  part.  This 
part  may  be  deflected  from  its  course  by  a  smooth  surface, 
and  collected  by  a  lens,  showing  that  it  possesses  in  com- 
mon with  light  the  properties  of  reflection  and  refraction. 
It  differs  from  light  only  in  being  invisible.  Its  waves 
are  longer  and  vibratory  motion  slower  than  the  luminous 
parts  of  the  spectrum.  The  waves  and  vibrations  are  not 
of  the  requisite  length  and  frequency  to  affect  the  optic 
nerve.  That  is  to  say,  there  is  nothing  in  the  organ  of 
sight  to  respond  to  waves  and  vibrations  of  this  length 
and  rate. 
11 


108  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

The  effect  of  radiant  heat  from  the  sun,  both  lumi- 
nous and  non-luminous,  is  well  known  to  all.  No  arti- 
ficial heat  can  take  the  place  of  solar  heat.  The  sanitary 
beneficence  of  sunshine  is  proverbial.  It  is  reasonable 
now  to  suppose  that  the  form  of  artificial  heat  which 
most  nearly  resembles  solar  heat  is  most  healthful.  All 
bodies  radiate  heat.  If  two  bodies  are  separated  by  noth- 
ing but  air,  each  is  constantly  receiving  heat  from  the 
other,  but  if  one  is  of  a  higher  temperature  than  the  other 
the  hotter  body  will  radiate  more  than  it  receives,  while 
the  cooler  body  will  radiate  less  than  it  receives  ;  hence, 
by  this  process  of  exchange,  the  heat  of  the  two  bodies 
will  become  equalized.  The  air  between  the  bodies  will 
not  be  affected  by  the  radiant  heat  of  either,  and  this  is 
equally  true  whether  the  radiant  heat  is  luminous,  as 
from  an  open  fireplace,  or  non-luminous,  as  from  stoves 
.or  heated  pipes. 

Radiant  heat  is  transmitted  in  straight  lines,  and,  like 
light,  diminishes  in  intensity  as  the  square  of  the  distance 
from  the  source  of  heat  increases.  It  passes  through  the 
air  without  affecting  it,  but  heats  all  solid  bodies  upon 
which  it  strikes.  Tyndall,  by  a  series  of  experiments,  has 
concluded  that  vapor  of  water  in  the  atmosphere,  if  in 
considerable  quantity,  intercepts  the  passage  of  radiant 
heat,  and  to  such  a  degree  as  almost  to  make  a  humid  air 
opaque  to  radiant  heat.  This,  however,  has  not  been 
verified  by  other  experiments. 

The  air  of  a  room  heated  by  radiation  can  not  be  ac- 
curately tested  by  a  thermometer,  as  the  bulb  receives 
radiant  heat,  while  the  air  surrounding  it  remains  cool. 
To  prevent  this,  the  bulb  should  be  surrounded  by  a 
bright  piece  of  tin,  to  reflect  away  the  radiant  heat. 

One  advantage  of  radiant  heat  is.  that  it  warms  the 
body  and  the  objects  in  the  rooin  without  heating  the  air 


WARMING.  109 

we  breathe.  An  accompanying  disadvantage  is  that,  in 
ordinary  heating  by  radiation,  especially  that  of  the  fire- 
place, the  radiant  heat  can  warm  but  one  side  of  the  body 
at  the  same  time.  There  is  no  doubt  that  if  the  body 
could  receive  sufficient  radiant  heat  to  warm  it  on  all 
sides  an  atmospheric  temperature  of  50°  would  be  more 
healthful  than  a  higher  one. 

Radiant  heat  is  believed  to  possess  peculiar  sanitary 
virtues,  and  we  have  seen  good  reasons  for  this  belief. 
Some  writers  even  express  the  relative  values  of  con- 
ducted, radiant,  and  convected  heat  by  characterizing 
radiant  heat  as  "golden,"  conducted  heat  as  "silver," 
and  convected  heat  as  "  copper."  From  the  earliest 
times  the  open  fire  has  been  instinctively  felt  to  possess 
special  virtue.  The  peculiar  exciting  glow  produced  by 
the  fireplace  is  the  common  experience  of  everybody.  Its 
peculiar  virtue  is  not  alone  in  abstracting  foul  air  from 
the  room,  but  in  the  nervous  stimulus  of  direct  radial 
contact. 

The  relative  value  of  luminous  and  non-luminous  ra- 
diation is  not  known,  but  the>e  is  little  doubt  that  the 
former  far  exceeds  the  latter.  There  is  reason  for  this. 
The  luminous  heat  appeals  to  one  more  sense,  that  of 
sight,  and,  even  though  the  physical  qualities  of  the  two 
kinds  were  otherwise  the  same,  this  alone  might  materially 
modify  the  total  effect.  We  always  look  at  the  glowing 
grate,  and  are  never  indifferent  to  it.  The  direct  lumi- 
nous radiation  of  a  fireplace  is  the  best  substitute  for  sun- 
shine, and  the  direct  radiation  of  a  heated  body  is  proba- 
bly next  in  value.  It  will  be  seen,  however,  in  our  dis- 
cussion of  combined  methods  of  heating  and  ventilating, 
that  direct  radiation  alone  is  not  sufficient. 

Convection. — In  fluids,  such  as  air  and  water,  the 
composing  particles  are  free  to  move  among  one  another, 


HO  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

there  being  no  friction  or  cohesion  between  them.  When 
any  of  these  particles  become  heated  by  contact  with  a 
hot  body  they  expand,  decrease  in  density,  and  rise,  other 
particles  moving  in  to  fill  their  places.  The  circulation 
thus  caused  is  termed  convection.  Convection  is  not, 
like  radiation,  a  specific  kind  of  heat,  but  is  simply  a 
mode  of  heat-conveyance.  The  particles,  when  separately 
considered,  are  heated  by  conduction,  when  they  at  once, 
by  their  diminished  specific  gravity,  rise  and  give  place 
to  others  to  be  heated  in  the  same  manner.  The  process 
may  be  likened  to  a  large  number  of  pupils  crowded 
around  a  stove  ;  the  nearer  ones  become  warm,  fall  back 
and  give  place  to  the  others,  till  the  whole  number  be- 
come warmed.  It  is  by  convection  that  air  and  water  are 
heated.  Both  of  these  fluids  are  poor  conductors,  and 
were  it  not  for  the  lack  of  cohesion  between  their  parti- 
cles there  would  be  no  hope  of  warming  them.  Their 
non-conducting  property  may  be  proved  by  trying  to  heat 
them  from  the  top  downward.  If  ether  be  poured  on  the 
surface  of  water  it  may  be  burned  off  without  affecting 
the  bulb  of  a  thermometer  placed  half  an  inch  below  the 
surface  of  the  water ;  but  the  same  amount  of  heat  ap- 
plied at  the  bottom  of  the  containing  vessel  would  sensi- 
bly raise  the  temperature  of  the  whole  contents.  It  is 
evident,  then,  that  air  or  water  must  be  heated  at  the 
bottom. 

To  prevent  the  too  rapid  escape  of  heat,  warm  air  is 
sometimes  admitted  at  the  top  of  the  room,  and  drawn 
out  at  the  bottom  near  the  floor.  This  has  been  tried  in 
some  of  the  European  hospitals.  As  naturally  to  be  ex- 
pected, this  method  has  not  been  successful.  It  is  work- 
ing against  the  force  of  gravity  instead  of  with  it.  If 
accomplished  at  all,  it  must  be  at  the  expense  of  con- 
siderable power.  Hot  water  can  by  means  of  a  syringe 


METHODS  OF  WARMING.  HI 

be  forced  to  the  bottom  of  a  vessel  of  cold  water,  thus 
warming  it,  but  it  takes  power  to  do  it.  The  same  prin- 
ciple holds  when  dealing  with  air. 


CHAPTER  XVII. 

METHODS  OF  WARMIHG. 

THE  various  methods  of  warming  school-houses  will 
be  considered  in  connection  with  their  accompanying  pos- 
sibilities of  ventilation  ;  for  a  system  of  heating  the  air 
which  does  not  at  the  same  time  provide  for  its  necessary 
renewal  is  hardly  worthy  of  consideration  ;  such  meth- 
ods, therefore,  will  be  considered  only  to  expose  their 
defects,  that  they  may  the  sooner  give  place  to  better  ones. 

The  Open  Fireplace. — The  open  fire,  as  a  means  of 
heating,  is  coming  to  be  regarded  as  an  antiquated  insti- 
tution, which  very  well  answered  the  purpose  of  our  un- 
learned forefathers,  but  which  is  now  regarded  as  too 
primitive  for  this  age  of  steam,  hot  air,  and  patent  stoves. 
While  the  open  fire  still  has  a  limited  existence  in  private 
dwellings,  in  the  form  of  ornamental,  badly-constructed 
grates,  and  dummy  mantels,  it  is  no  longer  even  thought 
of  in  this  country  as  a  means  of  warming  school-houses. 
It  will  receive  attention  here,  not  as  an  historical  relic, 
but  partly  because  it  is  the  best  arrangement,  as  far  as  it 
goes,  for  the  combined  purpose  of  warming  and  ventilat- 
ing that  has  ever  been  devised,  and  partly  because  the 
best  school-house  in  the  world — the  City  of  London  High 
School — is  so  warmed,  ventilated,  and  made  comfortable. 

The  history  of  the  open  fireplace,  from  its  first  use  by 
the  Romans,  need  not  here  be  given  ;  we  are  interested 


112  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

only  in  that  form  of  it  which  best  conforms  to  the  prin- 
ciples of  heating  and  ventilating.     One  of  the  best  con- 


FIG.  16. 


structed  fireplaces  is  Dr.  Arnott's  smokeless  grate,  which 
may  be  understood  by  reference  to  Fig.  16.  The  chim- 
ney, rsuw,  is  of  the  usual  construction  ;  a b  ef  repre- 


METHODS  OF  WARMING.  113 

sent  the  front  bars  of  a  bottomless  grate,  it  being  open 
for  the  admission  of  coal,  and  needs  to  be  supplied  only 
once  a  day.  The  fire  is  lighted  by  laying  on  the  surface  of 
the  coal,  at  ef,  a  sufficient  quantity  of  light  wood  to  insure 
ignition.  The  coal  below  becomes  heated  ;  the  bitumen 
rises  and  burns.  As  the  fire  burns  low,  it  is  raised  by 
means  of  a  lever,  h,  working  in  the  notched  bar  I,  which 
pushes  up  a  false  bottom  s  s,  upon  which  the  coal  rests. 
The  fire  is  supported  by  air  which  passes  through  the 
bars  in  front ;  v  represents  a  valve  or  damper  in  the  wall 
near  the  ceiling,  and  regulates  an  opening  into  the  chim- 
ney. This  further  serves  as  a  ventilator,  and  may  be  con- 
trolled by  means  of  the  cord  x  suspended  within  easy 
reach.  In  ordinary  fireplaces  the  large  space  above  the 
fire  robs  the  room  of  much  of  its  pure  air,  which  mixes 
with  the  smoke  in  large  quantities  and  passes  up  the 
chimney.  This  is  prevented  in  the  grate  now  under  con- 
sideration by  a  device,  here  described  in  Dr.  Arnott's  own 
words  :  "  The  whole  of  the  air  so  contaminated,  and 
which  may  be  in  volume  twenty,  fifty,  or  even  a  hundred 
times  greater  than  that  of  the  true  smoke  or  burned  air, 
is  then  all  called  smoke,  and  must  all  be  allowed  to  as- 
cend away  from  the  room,  that  none  of  the  true  smoke 
may  remain.  It  is  evident,  then,  that  if  a  cover  or  hood 
of  metal  be  placed  over  a  fire,  as  represented  by  T  in  the 
diagram,  or  if,  which  is  better,  the  space  over  the  fire  bo 
equally  contracted  by  brickwork,  so  as  to  prevent  the 
diffusion  of  the  true  smoke  or  the  entrance  of  pure  air 
from  around  to  mix  with  it,  except  just  what  is  necessary 
to  burn  the  inflammable  gases  which  arise  with  the  true 
smoke,  there  will  be  a  great  economy.  This  is  done  in 
the  new  fireplace,  with  a  saving  of  from  one  third  to 
one  half  of  the  fuel  required  to  maintain  a  desired  tem- 
perature. In  a  room  the  three  dimensions  of  which  are 


VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

15  feet,  13£  feet,  and  12  feet,  with  two  large  windows, 
the  coal  burned  to  maintain  a  temperature  of  65°  in  cold 
winter  days  has  been  18  pounds  for  19  hours,  or  less  than 
a  pound  an  hour." 

The  room  here  supposed  has  about  one  fourth  the  ca- 
pacity of  an  ordinary  school-room.  This  fireplace  would 
then,  according  to  Dr.  Arnott,  warm  a  school-room  with 
less  than  4  pounds  of  coal  per  hour.  But  we  found  by  a 
previous  calculation  that  about  18  pounds  are  necessary 
when  the  conditions  of  ventilation  are  all  provided  for 
and  the  temperature  to  be  raised  is  35°.  It  would  appear 
from  this  great  difference  that,  after  making  due  allow- 
ance for  the  four  extra  windows  and  for  the  rigor  of  our 
climate  over  that  of  England,  a  form  of  open  fire,  such 
as  that  just  described,  is  as  economical  as  other  modes  of 
heating. 

Heat  is  further  economized  in  Boyd's  open  fireplace, 
by  means  of  which,  in  addition  to  Dr.  Arnott's  plan,  the 
cold  fresh  air  is  admitted  from  the  outside  to  a  chamber- 
box  just  back  of  the  fire.  This  being  put  in  communica- 
tion with  the  room  furnishes  an  inlet  of  pure  warm  air. 
It  is  this  kind  of  fireplace  which  is  used  in  the  magnifi- 
cent high-school  building  of  London,  which  has  only 
recently  been  finished.  Further  provision  was  made  in 
the  construction  of  this  school-house  in  making  foul-air 
openings  near  the  ceiling  and  leading  to  a  mammoth  as- 
pirating chimney  extending  to  the  basement.  For  the 
open  fireplaces  a  separate  flue  is  provided  for  each  room 
independent  of  all  the  others. 

In  a  climate  in  which  the  heat  thns  supplied  is  suffi- 
cient, this  plan  is  about  as  nearly  ideally  perfect  as  can  be 
imagined.  Here  the  room  is  heated  by  convection  of  the 
ascending  warm  currents  rising  from  the  fire,  by  that 
which  comes  in  from  behind  the  grate,  and,  best  of  all, 


METHODS  OF  WARMING.  115 

by  the  direct  radiation  of  live  luminous  heat  direct  from 
the  open  fire.  The  fresh  air  is  warmed  before  entering, 
without  being  overheated.  The  room  is  ventilated  both 
from  the  top  and  from  the  bottom  of  the  room.  The 
C02,  and  other  respired  impurities,  always  at  the  top 
of  the  room,  are  drawn  off  by  the  aspirating  chimney. 
Other  foul  colder  gases,  from  the  floors  and  neighboring 
closets,  which  may  be  lurking  in  the  lower  strata  of  the 
air,  are  effectually  drawn  off  by  the  draft  of  the  fireplace. 

Whether  this  mode  of  warming  would  be  adequate  for 
the  coldest  days  of  an  American  winter  is  not  known.  It 
has  never  been  tried.  But  it  is  safe  to  presume  that  it 
would  be  sufficient  for  nine  tenths  of  the  time  in  which  a 
fire  is  needed.  In  severe  weather  it  could  be  supple- 
mented with  steam-pipes,  of  which  more  hereafter. 

Stoves. — Everybody  who  reads  this  book  knows  what 
a  stove  is,  hence  no  general  definition  need  be  given.  As 
a  means  of  warming,  a  stove  may  be  good  or  bad,  according 
as  the  principles  which  should  govern  warming  and  ven- 
tilation are  conformed  to  or  violated.  As  the  latter  prac- 
tice is  more  common,  stoves  are  growing  into  general  dis- 
favor. 

The  necessary  conditions  governing  the  selection  of  a 
stove  are :  1.  It  must  be  large,  having  sufficient  surface 
to  warm  sufficiently  without  overheating.  The  evils  of 
overheating  the  air  have  already  been  referred  to  in 
another  place,  and  it  may  be  here  emphasized  that  air 
coming  in  contact  with  a  highly-heated  surface  is  ruined 
for  purposes  of  respiration.  The  peculiarly  disagreeable 
odor  of  such  air  is  probably  due  to  a  charring  of  the  or- 
ganic matter  contained  in  the  air.  The  relative  humidity 
of  such  air  is  so  low  that  it  is  rendered  not  only  unfit  for 
respiration  but  ruinous  to  all  animal  tissue  with  which  it 
comes  in  contact.  2.  A  stove  should  be  lined  with  fire- 


116  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

brick,  or  other  similar  material,  to  intercept  poisonous 
gases  which  would  otherwise  pass  through  the  heated 
iron  into  the  room  and  contaminate  the  air.  3.  It  should 
combine  or  be  accompanied  with  some  efficient  means 
of  ventilation.  4.  The  smoke-pipe  should  be  long,  taking 
a  turn  around  the  room  so  as  to  economize  the  heat. 

These  requirements  being  complied  with,  there  is  lit- 
tle objection  to  the  use  of  stoves.  On  the  contrary,  there 
is  much  in  favor  of  them.  In  point  of  economy  it  is 
the  cheapest  means  of  warming  known.  But  where  the 
requirements  just  enumerated  are  not  observed — when 
stoves  are  small,  without  lining,  often  heated  to  redness, 
and  without  means  of  ventilation — they  are  not  only  use- 
less but  become  engines  of  destruction.  Hundreds  of 
different  kinds  of  stoves  are  in  use,  but  I  shall  specify 
no  further  than  is  necessary  to  illustrate  the  correct  ap- 
plication of  underlying  principles.  After  canvassing  the 
whole  ground,  I  return  to  Dr.  Arnott,  who  understood 
principles,  and  knew  how  to  apply  them.  Fig.  17  illus- 
trates the  Arnott  closed  stove,  and  is  thus  described  by 
him  :  "  The  complete  self-regulating  stove  may  indeed 
be  considered  as  a  close  stove  with  an  external  case,  and 
certain  additions  and  modifications  to  be  described.  The 
dotted  lines  and  the  small  letters  mark  the  internal  stove, 
and  the  entire  lines  the  external  case  or  covering.  The 
letters  A  B  C  D  mark  the  external  case,  which  prevents 
the  intense  heat  of  the  inner  stove,  a  b cd,  from  damaging 
the  air  of  the  room.  F  is  the  regulating  valve  for  ad- 
mitting the  air  to  feed  the  fire  (see  Fig.  4).  It  may  be 
placed  near  the  ashpit-door,  or  wherever  more  convenient. 
The  letters  //  mark  the  fire-brick  lining  of  the  fire-box 
or  grate,  which  prevents  such  cooling  of  the  ignited  mass 
as  might  interfere  with  steady  combustion.  H  is  a  hop- 
per or  receptacle  with  open  mouth  below,  suspended  above 


METHODS   OF  WARMING. 


117 


the  fire  like  a  bell,  to  hold  a  sufficient  charge  of  coal  for 
twenty-four  hours  or  more,  which  coal  always  falls  down 

FIG.  17. 


of  itself,  as  that  below  it  in  the  fire-box  is  consumed.  The 
hopper  may  at  any  time  be  filled  with  coal  from  above 
through  the  lid  K,  of  the  hopper,  and  the  other  lid  K'  of 
the  outer  case.  These  lids  are  rendered  nearly  air-tight 
by  sand-joints ;  that  is,  by  their  outer  edges  or  circumfer- 
ence being  turned  down  and  made  to  dip  into  grooves  filled 
with  sand  at  e  e.  The  burned  air  or  smoke  from  the  fire 


118  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

rises  up  in  the  space  between  the  hopper  and  the  inner 
stove-case,  to  pass  away  by  the  internal  flue  x  into  the 
other  flue  X  of  the  outer  case.  L  is  the  ash-pit  under  the 
fire-bars  ;  Gr  is  the  ash-pit  door,  which  must  be  carefully 
fitted  to  shut  in  an  air-tight  manner  by  grinding  its  face 
or  otherwise.  The  coal  is  intensely  ignited  below  where 
the  fresh  air  maintains  combustion,  but  colder  gradually 
as  it  is  further  up.  Only  the  coal  in  the  fire-grate  below, 
where  the  fresh  air  has  access  to  it  through  the  fire-bars, 
can  be  in  a  state  of  active  combustion." 

This,  it  will  be  observed,  is  the  origin  of  the  modern 
"  base-burner,"  which  is  a  somewhat  degenerated  modifi- 
cation. Modern  stove-mongers  study  for  ornament  rather 
than  utility. 

To  be  complete  as  a  ventilator,  furnishing  an  abun- 
dance of  pure  warmed  air,  the  space  between  the  inner 
and  outer  stove-cases  should  be  in  connection  with  the 
outside  air  by  means  of  an  air-duct,  in  which  there  would 
be  found  an  inflowing  current  as  the  air  rises  in  becoming 
heated.  The  outer  flue  X  should  be  open  into  the  room 
in  order  that  this  warmed  air  may  be  utilized.  This  was 
not  the  intent  of  Dr.  Arnott,  as  he  supposed  the  air  in 
contact  with  the  inner  case  to  be  vitiated  by  excessive 
heating.  But  the  stove  could  easily  be  made  of  such  a 
proportion  between  the  size  of  the  coal-hopper  and  the 
weight  and  surface  of  iron  used  in  the  construction  of 
the  cases  as,  together  with  the  cold-air  connection,  to  pre- 
vent overheating. 

A  very  simple,  effective,  and  inexpensive  stove  is  il- 
lustrated by  Fig.  18.  F  represents  a  stove  of  ordinary 
construction,  upon  which  is  placed  a  large  double  drum, 
the  outer  part,  F,  of  which  is  in  connection  with  the  fire, 
and  conducts  away  the  smoke  and  waste  products  through 
the  pipe  P.  The  inside  drum  A  communicates  with  the 


METHODS   OF   WARMING. 


119 


outside  air  by  the  duct  D.    The  size  of  the  drum  and  the 
length  of  the  pipe  P  should  be  such  as  to  utilize  all  the 


FIG.  18. 


heat  before  the  chimney  is  reached.     The  action  is  sim- 
ple.    As  the  air  inside  the  drum  becomes  heated  by  the 
fire-draft  aronnd  it,  it  expands,  rises,  and  passes  out  at  B 
12 


120  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

into  the  room.  The  partial  vacuum  thus  formed  is  filled 
with  inflowing  cold  air  through  the  duct  D.  If  desired, 
an  upper  room  may  be  heated  by  the  same  fire  by  extend- 
ing the  pipe  P  through  the  ceiling,  enlarging  it  in  the 
room  above  into  a  drum  of  the  same  construction  as  the 
one  described.  A  patent  was  granted  in  1884  to  A.  M. 
Hicks  and  A.  Dishman,  of  Kentucky,  for  the  invention 
of  a  stove  of  similar  construction. 

Stoves,  while  not  the  best  means  of  warming,  may  by 
a  little  care  and  attention  be  made  serviceable  and  eco- 
nomical. Considering  their  comparative  simplicity  and 
easy  adjustment,  and  the  qualifications  of  the  average 
builder,  it  is  questionable  whether  it  would  not  in  the 
majority  of  cases  be  better  to  make  use  of  improved  stove 
heating  than  tamper  with  those  more  improved  systems, 
the  adjustment  and  management  of  which  require  scien- 
tific knowledge  and  technical  skill.  A  fairly  good  system 
properly  managed  is  better  than  a  more  excellent  one  in 
unskillful  hands. 

Many  forms  of  open  stoves  have  recently  been  made, 
intended  to  combine  the  advantages  of  the  closed  stove 
and  the  open  fireplace  ;  among  which  may  be  mentioned 
the  so-called  "  Baltimore  Heater."  It  consists  of  an  open- 
front  stove  set  back  into  a  chimney  recess  resembling  the 
common  fireplace.  The  smoke-pipe  extends  up  through 
the  entire  length  of  the  chimney,  leaving  the  space  be- 
tween it  and  the  inside  walls  of  the  chimney  as  a  venti- 
lating flue  which  may  be  put  in  communication  with  the 
room. 

TJie  Ruttan  System. — Stoves  may  be  greatly  enlarged 
and  placed  in  a  separate  apartment,  preferably  a  basement, 
where  they  are  made  to  furnish  the  heat  to  the  various 
parts  of  a  building  by  means  of  communicating  tubes. 
They  are,  when  so  situated,  sometimes  called  furnaces. 


METHODS  OF  WARMING.  121 

Many  different  kinds  of  furnaces  are  in  use  for  thus  sup- 
plying rooms  with  hot  air,  all  having  for  their  object  the 
heating  of  air  and  transferring  it  to  the  various  rooms. 
Many  of  these  furnaces  are  constructed  with  the  sole 
object  of  heating,  no  provision  being  made  for  ventila- 
tion. Some  of  these  fulfill  their  object  well,  but,  as  it  is 
not  the  purpose  here  to  consider  the  merits  of  heaters 
simply  as  such,  they  will  not  be  discussed. 

The  most  which  has  been  accomplished  in  the  way  of 
warming  by  means  of  hot  air,  where  ventilation  at  the 
same  time  has  not  been  ignored,  has  been  done  by  the 
so-called  Ruttan  system.  This  system  of  heating  and 
ventilating  is  coming  into  quite  extensive  use  in  Canada 
and  many  of  the  Northern  States,  where  it  is  receiving 
many  testimonials  of  approval. 

For  some  of  the  excellent  features  which  this  system 
undoubtedly  possesses,  and  for  some  of  the  overdrawn  esti- 
mates of  its  merits  made  by  its  friends,  its  merits  and 
demerits  will  here  be  considered.  The  system  combines 
the  patented  inventions  of  Henry  Euttan,  of  Canada ;  J. 
D.  Smead,  of  Toledo,  Ohio ;  and  B.  R.  Hawley.  For 
heating,  the  tubular  furnace  is  used,  which,  on  account 
of  the  large  surface  which  is  thus  brought  in  direct  con- 
tact with  the  fire,  is  economical  as  a  consumer,  and  the 
large  surface  which  is  also  subjected  to  the  air  makes  it 
effective  as  a  heater.  It  conforms  well  to  the  require- 
ments of  a  heater  which  have  already  been  insisted  on 
under  the  discussion  of  stoves.  The  fire-box,  by  its  con- 
struction, presents  a  large  surface  to  the  fire  and  to  the 
air.  The  surface  is  further  increased  by  causing  the 
smoke  and  burned  products  to  pass  successively  through 
the  tubes.  The  furnace  is  set  into  masonry,  into  which 
the  cold  air  is  admitted  for  warming,  and  passes  out  at 
the  tubes  to  the  rooms.  The  method  of  admitting  the 

6 


122  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

heated  air  into  the  room  is  embodied  in  an  invention  of 
Mr.  Smead,  patented  by  him  in  1882.  It  may  be  under- 
stood by  reference  to  Fig.  19,  which  represents  a  vertical 

FIG.  19. 


transverse  section  through  the  heater  and  lower  part  of 
one  of  the  flues.  A  represents  the  building,  B  the  air- 
flue,  C  the  heating  chamber,  D  the  cold-air  duct,  E  the 


METHODS  OF  WARMING.  123 

furnace  chamber,  F  a  wall  separating  the  furnace  from  the 
flues,  G  an  opening  from  the  furnace  into  the  flue,  H  the 
opening  from  cold-air  duct  into  the  flue,  I  a  hinged  valve 
for  regulating  the  relative  supply  of  hot  and  cold  air,  J 
the  opening  into  the  room  to  be  warmed,  L  a  hand-knob 
for  raising  and  lowering  the  valve  I,  d  a  weight  to  hold 
the  valve  in  position.  The  arrows  show  the  direction  of 
the  air.  The  action  of  this  arrangement  is  as  follows: 
The  air  in  the  chamber  C  becomes  heated,  rises  and  passes 
up  the  flue  M,  and  into  the  room  through  J.  The  cold 
air  flows  in  at  D  to  fill  the  partial  vacuum  thus  made. 
When  the  room  becomes  too  warm,  the  inflowing  hot  air 
is  mixed  with  cold  air  by  turning  the  knob  L,  which 
raises  the  valve  I,  closing  the  hot-air  passage  G  and  open- 
ing the  cold-air  passage  B.  The  height  to  which  this  valve 
is  raised  regulates  the  relative  size  of  the  hot-  and  cold- 
air  openings.  It  will  be  well  at  this  point  to  notice  that, 
while  the  relative  size  of  the  hot-  and  cold-air  openings 
may  be  thus  regulated,  it  is  doubtful  whether  the  same 
proportions  maintain  between  the  hot  and  cold  air  pass- 
ing through  them.  The  quantity  of  inflowing  hot  air 
may  undoubtedly  be  regulated  by  this  valve,  by  opening 
and  closing  it :  but  how  the  cold  air  is  to  rise  and  flow  in 
its  place  is  not  so  clear.  Suppose  the  valve  be  raised  so 
as  to  make  the  size  of  the  hot-  and  cold-air  openings 
equal,  what  will  then  be  the  action  ?  The  hot  air  rising 
through  the  flue  has  a  vacuum-forming  tendency,  and  it 
is  supposed  by  the  inventor  that  the  cold  air  at  the  bottom 
of  the  flue  will  rise  up  to  fill  the  partial  vacuum.  This  it 
might  do  were  there  not  a  source  of  supply  by  which  the 
vacuum  is  supplied  with  less  resistance.  There  is  an  in- 
exhaustible supply  of  hot  air  coming  from  the  furnace, 
already  possessing  a  tendency  to  rise,  and  half  closing  the 
hot-air  opening,  as  in  the  case  supposed,  further  increases 


124:  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

the  tension  of  the  hot  air  thus  resisted  as  it  rises  from  the 
furnace.  Will  not,  then,  this  supply  of  hot  air  with  high 
tension  be  sufficient  to  supply  all  vacuum  which  the  air 
rising  in  the  flue  will  create  ?  If  the  cold  air  will  rise 
under  these  conditions,  it  is  difficult  to  see  why  the  cold 
air  of  the  room  into  which  the  warm  air  enters  will  not 
rise  along  with  and  be  drawn  up  by  it  as  it  passes  in  at  J 
and  rises  to  the  top  of  the  room. 

This  is  not  a  case  parallel  with  the  aspirating  chim- 
ney, where  hot  air  rising  in  a  shaft  will  cause  cooler  air 
to  flow  in  through  openings  into  it.  In  this  case  the 
partial  vacuum  has  no  other  adequate  source  of  supply, 
which  we  have  seen  is  not  the  case  in  the  flue  under 
consideration. 

It  is  not  here  maintained,  however,  that  this  valve  is 
useless  ;  on  the  contrary,  it  may  be,  under  certain  con- 
ditions, very  useful.  If  it  be  nearly  or  quite  raised,  so  as 
to  shut  off  most  or  all  of  the  hot  air,  and  if  there  is  a 
good  aspirating  chimney  drawing  the  foul  air  from  the 
room  which  is  being  supplied,  and  if  the  doors  and  win- 
dows are  carefully  closed,  then  the  cold  air  will  rise  in 
this  cold-air  duct.  But  it  is  safe  to  conclude  that  all 
these  conditions  are  necessary.  If  there  is  no  aspi- 
rating chimney  there  will  be  no  vacuum-forming  tendency 
in  the  room  sufficient  to  cause  cold  air  to  rise.  If  a  door 
or  window  is  opened,  the  draft  in  all  cold-air  ducts  imme- 
diately ceases,  as  air,  like  all  other  moving  bodies,  seeking 
the  line  of  least  resistance,  will  come  from  a  source  where 
it  is  least  opposed  ;  and  through  an  open  door  or  window 
the  resistance  by  friction  is  nothing,  while  in  the  cold-air 
flue  it  is  considerable.  Here,  let  it  be  observed,  is  another 
argument  for  double  windows  and  spring-closing  doors. 

In  the  Kuttan  system  the  foul  air  is  drawn  out  of  the 
room  from  the  bottom  through  registers  near  the  floor. 


METHODS   OF   WARMING.  125 

These  outlets  are  placed,  when  convenient,  on  the  sides 
of  the  room  opposite  the  final  outlet,  so  that  foul  warm 
air,  as  it  leaves  the  room,  will  pass  under  the  floor  which 
it  is  thus  intended  to  warm.  The  foul  air  thus  passing 
from  the  different  rooms  is  all  collected  into  a  foul-air 
room  adjacent  to  the  smoke-chimney,  into  the  bottom 
of  which  it  communicates  by  a  large  opening. 

The  theory  of  the  system  may  be  summarized  as  fol- 
lows :  The  air  warmed  by  the  furnace  rises  through  the 
air-flue  into  the  room,  where,  within  convenient  reach,  a 
hand-knob  is  placed  for  regulation  of  hot  and  cold  air. 
The  warm  air,  after  its  admission,  rises  to  the  top  of  the 
room  which,  on  being  filled  from  the  top  downward, 
presses  the  cold  air  down  and  out  of  the  outlets.  The 
foul  air,  it  is  claimed,  being  "  at  the  bottom,"  is  thus 
drawn  off,  and  the  upper  part  of  the  room  kept  constantly 
filled  with  pure  warm  air.  The  floor  is  warmed  by  the 
foul  air  as  it  passes  beneath  on  its  way  out.  This  foul  air 
is  kept  in  motion  by  the  draft  of  the  chimney  into  which 
the  foul-air  room  opens.  It  may  be  said  in  favor  of  this 
system  that  it  shows  throughout  a  studied  effort  toward 
conformity  to  physical  laws,  and  is  therefore  a  valuable 
contribution  toward  the  solution  of  the  difficult  and  all- 
important  problem  of  ventilation.  It  is  an  ingenious 
system,  and  is  doing  comparatively  good  service.  The 
critical  review  to  which  it  will  now  be  submitted  is  in- 
tended to  be  in  the  interest  of  truth  and  the  public  good, 
and  toward  suggesting  improvements  rather  than  con- 
demning the  system. 

In  the  first  place,  considering  the  large  amount  of 
friction  which  the  air  necessarily  encounters  in  finding 
its  way  out,  and  the  rapid  passage  of  air  which  is  neces- 
sary to  secure  proper  ventilation,  a  higher  degree  of  fur- 
nace heat  is  necessary  than  is  harmless  to  the  air. 


126  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

Again,  if  the  air  entered  the  room  at  the  temperature 
of  comfort,  as  claimed  in  the  theory,  it  would  be  too  cold 
to  be  endured  after  having  made  its  circuit  to  the  top  of 
the  room  and  settled  down  to  the  point  of  utilization. 

These  two  reasons  make  the  overheating  of  the  air 
unavoidable.  We  have  seen  that  overheated  air  is  dam- 
aged for  purposes  of  respiration ;  and  it  is  evident  that 
the  heat  necessary  to  raise  air  to  a  high  temperature  is 
nearly  all  lost,  as  this  surplus  heat  must  pass  away  through 
walls  and  windows  in  cooling  down  to  the  degree  of  com- 
fort. 

The  origin  of  this  difficulty  seems  to  be  in  the  lack  of 
proper  distribution  of  the  air  as  it  enters  the  room.  When 
the  incoming  air  is  all  at  one  place,  it  will  of  course  rise 
to  the  top  of  the  room  before  it  becomes  sufficiently 
vitiated  to  allow  its  escape  before  it  has  been  used.  It 
must  therefore  be  retained,  but  it  can  not  be  retained 
without  placing  the  outlets  below.  If  the  air  was  prop- 
erly distributed  as  it  enters,  it  would  be  sufficiently  viti- 
ated to  be  allowed  to  pass  out  at  the  top  of  the  room,  on 
reaching  that  point,  the  natural  place  for  its  exit. 

The  placing  of  the  outlets  below  is  further  justified, 
by  the  theory  of  this  system,  in  supposing  the  vitiated  air 
is  at  the  bottom  of  the  room.  The  fallacy  of  this  assump- 
tion is  shown  in  another  place,  under  the  consideration  of 
the  position  of  outlets,  and  need  not  be  repeated  here. 

A  condition  of  things  may  exist,  and  probably  does  in 
this  system,  where  the  most  of  the  uudiffused  C02  occu- 
pies a  position  somewhat  near  the  breathing  line.  If  the 
incoming  air  is  warmer  than  the  breath — about  95° — it 
will  rise  above  the  breath  and  prevent  its  ascent  higher 
than  that  stratum  of  air  having  a  temperature  of  95°.  In- 
stead, therefore,  of  making  a  dive  for  the  floor,  the  re- 
spired breath,  carrying  C08  and  organic  matter,  will  rise 


METHODS  OF  WARMING.  127 

a  short  distance,  and,  before  passing  out  of  the  room, 
must  again  cross  the  breathing  line.  Now,  the  shorter 
the  distance  between  this  stratum  and  the  breathing  line, 
the  less  opportunity  for  diffusion  to  take  place  in  time  to 
prevent  rebreathing  the  expired  impurities. 

An  objection  to  the  arrangement  for  warming  the  floor 
might  reasonably  be  urged  in  the  fact  that  so  large  a  part 
of  the  building  is  submitted  to  the  contamination  of  foul 
air  with  no  provision  for  cleansing.  The  walls  of  a  shaft 
or  rooiri  in  which  there  exist  large  quantities  of  air  viti- 
ated by  respiration  soon  become  coated  with  an  offensive 
and  poisonous  accumulation  of  organic  matter  which,  if 
not  removed,  is  liable  to  contaminate  the  entire  building, 
and  in  case  of  temporary  reversal  of  the  draft,  as  is  some- 
times sure  to  take  place  in  warm  weather,  when  little  or 
no  fire  is  required,  the  air,  in  passing  over  this  foul  mat- 
ter, becomes  unfit  for  respiration  before  it  reaches  the 
room.  All  foul-air  passages  should  be  accessible  to  the 
brush  of  the  janitor. 

One  obstacle  in  the  way  of  this  system  is  the  difficulty 
of  managing  the  average  builder.  In  order  that  the  pos- 
sibilities of  the  system  may  be  realized,  buildings  must 
be  constructed  from  the  beginning  with  special  design  for 
its  application.  In  buildings  not  specially  constructed 
for  this  system  it  is  practically  worthless,  and  the  same 
is  true  in  buildings  improperly  designed  for  it  by  design- 
ers who  do  not  fully  understand  the  principles  which  the 
system  requires  of  them  to  materialize.  This  is  in  itself 
no  fault  of  the  system,  but  is,  in  the  present  state  of  me- 
chanical service,  an  inevitable  obstacle. 

It  is  not  unfrequent  to  see  school-houses  built  for  this 
system  where  the  construction  ignores  the  very  principles 
upon  which  the  success  of  the  system  mainly  depends. 
In  one  instance  which  I  now  have  in  mind,  and  which  I 


128  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

had  excellent  opportunities  of  observing,  the  foul-air  out- 
lets led  to  single  chimneys  for  each  room,  which  were 
closed  up  solid  at  the  bottom,  and  unconnected  with  the 
smoke-chinmey  or  other  source  of  heat.  The  windows 
were  numerous  and  loosely  fitted,  which  allowed  the  hot 
air  to  pass  out  at  the  top  of  them  before  it  arrived  at  a 
point  low  enough  to  be  utilized.  The  small  dummy  aspi- 
rating chimneys,  having  little  draft,  failed  in  their  legiti- 
mate function  of  removing  the  foul  air  of  the  room 
in  order  to  give  place  to  the  incoming  hot  air,  which 
could  not  otherwise  find  an  entrance  sufficient  to  warm 
the  room.  These  circumstances  admitted  of  but  one 
result.  The  hot  air,  all  that  could  be  forced  to  enter, 
found  a  lodgment  in  the  upper  part  of  the  rooms,  where 
a  temperature  of  about  200°  was  maintained,  while  at  the 
floor  it  was  little  above  the  freezing  point.  Of  course  the 
apparatus  had  to  be  taken  out. 

In  conclusion,  it  may  be  said  of  the  Euttan  system 
that,  if  the  requirements  of  the  theory  be  carefully  con- 
formed to  in  the  construction  of  the  buildings,  the  win- 
dows and  doors  made  tight-fitting  and  kept  closed,  it 
will  work  comparatively  well,  yet  even  at  its  best  it  has 
inherent  defects  which  must  be  recognized  and  met  be- 
fore it  can  be  received  as  a  perfect  system. 


STEAM  HEATING.  129 

CHAPTER  XVIII. 

STEAM  HEATING. 

IN  heating  with  steam,  water  is  converted  into  steam 
in  a  boiler  heated  by  a  furnace  situated  in  the  basement 
or  other  convenient  locality.  The  steam  is  then  conveyed 
by  means  of  pipes  to  the  parts  of  the  building  to  be 
warmed. 

It  will  be  seen  by  a  careful  reading  of  the  foregoing 
pages  that  one  of  the  chief  defects  in  all  systems  of  warm- 
ing and  ventilating  so  far  considered  is  the  inadequate 
distribution  of  the  warmed  air.  This  is  a  matter  of  prime 
importance.  Heat  should  be  furnished  not  only  of  the 
necessary  amount,  but  it  should  be  furnished  in  such  a 
manner  that  it  can  be  utilized. 

We  have  seen  that  it  is  impossible  thoroughly  to  do 
this  by  stoves  and  hot-air  furnaces  in  buildings  more 
than  one  story  in  height.  If  our  school-houses  could  be 
confined  to  a  single  story,  furnace-warmed  air  might  be 
used,  and  perfect  ventilation  be  attained.  The  English 
House  of  Commons  is  heated  by  means  of  furnace- warmed 
air,  on  a  modified  plan  of  Dr.  Reid,  and  all  the  required 
conditions  of  ventilation  and  distribution  are  there  com- 
plied with.  But  the  same  results  would  not  be  possible 
in  an  upper  story  of  a  building. 

In  this  building  a  hot-air  chamber,  extending  beneath 
the  entire  floor,  supplies  the  room  with  warmed  air  ad- 
mitted through  a  perforated  floor.  Ventilation  is  at  the 
top,  and  the  foul-air  flues  have  their  opening  into  an  as- 
pirating chimney. 

In  buildings  of  several  stories,  containing  many  rooms, 
the  difficulties  of  heat  distribution  without  waste  are  met 
by  the  use  of  steam.  This  is  inevitable  from  the  natural 


130  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

properties  which  steam  possesses.  A  correct  popular  un- 
derstanding of  these  properties  would  eventually  settle 
the  question  as  to  the  best  method  of  warming  large 
school-buildings.  While  these  properties  are  easy  of  dem- 
onstration, it  is  curious  what  erroneous  notions  are  cur- 
rent concerning  them. 

Of  course  it  can  not  be  expected  that  the  printed  ad- 
vertisements prepared  by  furnace-heating  companies  will 
contain  much  that  is  scientifically  reliable  concerning  the 
peculiar  heating  advantages  of  steam  ;  and  while  it  might 
be  pertinent  to  ask  why  they  do  not  remain  silent  regard- 
ing that  which  they  either  misrepresent  or  misunder- 
stand, it  may  perhaps  be  excused  as  a  sort  of  special 
pleading  which  has  come  to  be  regarded  as  legitimate  in 
advertising. 

But  this  is  not  the  only  source  of  published  error  con- 
cerning the  properties  of  steam.  A  single  instance  will 
suffice.  W.  C.  Whitford,  ex-Superintendent  of  Public 
Instruction  of  Wisconsin,  in  a  book  on  "Plans  and  Speci- 
fications of  School-Houses,"  in  referring  to  steam  heat- 
ing says  :  "A  very  considerable  percentage  of  the  force 
derived  from  the  heat  applied  to  the  water  in  generating 
steam  is  lost  in  expanding  and  driving  this  steam  along 
the  iron  pipes  or  through  the  radiators.  In  other  words, 
the  heat  of  the  burning  fuel  appears  in  part  in  mechani- 
cal action  and  not  in  temperature." 

That  this  mechanical  action  is  lost  is  a  somewhat 
strange  doctrine.  A  few  quotations  from  authors  who 
have  given  special  attention  to  physical  laws  will  be  suffi- 
cient to  stand  against  this  view. 

Gage,  in  his  "Physics,"  says:  "Heat  that  is  con- 
sumed in  liquefying  solids  and  vaporizing  liquids  is 
always  restored  when  the  reverse  change  takes  place.  .  .  . 
The  fact  that  steam  in  condensing  generates  a  large 


STEAM   HEATING.  131 

amount  of  heat  is  turned  to  practical  use  in  heating 
buildings  by  steam." 

William  J.  Baldwin,  a  scientific  mechanical  engineer, 
in  his  work  on  "Steam  Heating  for  Buildings,"  says  : 
"  When  a  solid  becomes  a  liquid,  or  a  liquid  becomes  a 
vapor,  heat  is  absorbed  more  than  was  necessary  to  raise 
it  to  the  temperature  of  conversion,  and  this  latent  heat 
does  work  in  the  destruction  in  the  force  of  cohesion  and 
other  occult  changes  which  take  place,  and  must  be  ab- 
sorbed from  some  other  substance.  In  the  case  of  steam 
in  a  boiler,  it  comes  from  the  fuel  during  combustion, 
and  when  a  pool  of  water  is  vaporized  in  the  street,  it 
comes  from  the  sun  directly,  and  from  the  earth,  air,  etc., 
indirectly.  When  steam  or  vapor  is  condensed  this  same 
quantity  of  heat  that  was  received,  no  matter  where,  is 
given  off  to  any  substance  within  its  influence,  air,  water, 
etc.,  colder  than  itself,  and  it  is  this  property,  to  convey 
more  heat  within  ordinary  controllable  temperatures  than 
any  other  substance,  which  makes  water  and  its  vapor  so 
valuable." 

These  properties  of  steam  may  be  demonstrated  by  a 
simple  and  interesting  experiment : 

An  apparatus,  consisting  of  a  flask,  lamp  or  Bunsen 
burner,  bent  tube,  and  beaker,  is  arranged  as  shown  in 
Fig.  20.  Into  the  flask  A  pour  one  ounce  of  water  at 
32°  Fahr.,  and  into  the  beaker  C  pour  5£  ounces  at  the 
same  temperature.  In  a  short  time  the  water  in  A  will 
be  converted  into  steam,  which  will  pass  through  the  tube 
B  and  be  condensed  in  the  beaker  G.  Immediately  after 
the  total  evaporation  of  the  water  in  A,  the  water  in  C 
will  be  found  by  testing  to  be  at  a  temperature  of  212° 
Fahr.  By  carefully  noting  the  time  which  elapsed  from 
the  first  application  of  the  heat  till  boiling  commenced, 
and  also  from  when  boiling  commenced  till  the  evapora- 
13 


132  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

tion  was  completed,  it  will  be  found  that  the  latter  time 
is  5^  times  the  former,  that  it  requires  5^  times  as  long 


FIG.  20. 


to  convert  boiling  water  into  steam  as  it  does  to  raise 
water  from  the  freezing  to  the  boiling  point.* 

Now,  these  facts  teach,  first,  that,  as  the  application  of 
the  heat  is  constant,  5£  times  as  much  of  it  exists  as  la- 
tent heat  than  exists  as  sensible  heat.  During  the  entire 
process,  neither  the  boiling  water  nor  the  steam  acquires 
a  temperature  above  212°,  the  boiling-point  of  water. 
Second,  that  this  so-called  latent  heat  is  really  no  heat 
at  all,  but  mechanical  energy,  into  which  the  sensible 

*  To  avoid  accident  in  this  experiment,  the  flask  should  not  be  al- 
lowed to  boil  quite  dry,  as  this  would  cause  a  vacuum  to  be  formed  in 
the  flask,  which  would  suddenly  be  filled  by  a  rush  of  water  from  the 
beaker  through  the  tube.  To  avoid  a  similar  result,  the  tube  should 
always  be  raised  out  of  the  beaker  before  the  heat  is  removed,  for  if  the 
water  ceases  to  boil  the  steam  will  cease  to  be  driven  oflf,  and  a  vaccuum 
will  result  the  same  as  though  the  flask  were  allowed  to  boil  dry. 


STEAM  HEATING.  133 

heat  of  the  flame  was  converted  ;  this  energy  being  suffi- 
cient to  overcome  the  cohesion  between  the  particles  of 
the  water  and  to  transfer  them  against  gravity  over  into 
the  beaker.  Third,  that  as  the  water  in  the  beaker,  con- 
taining 5£  times  as  much  as  was  evaporated,  was  raised 
to  a  temperature  equal  to  the  highest  temperature  of  the 
steam,  this  latent  heat,  in  the  form  of  mechanical  energy, 
appears  as  sensible  heat  as  soon  as  condensation  takes 
place.  Fourth,  that  during  the  passage  of  the  steam, 
through  the  tube,  none  of  the  latent  heat  is  lost ;  that 
its  re-appearance  as  sensible  heat  is  reserved  until  the  in- 
stant of  condensation. 

In  view  of  these  principles,  practical  insight  need  not 
be  very  far-reaching  to  see  the  great  advantage  possessed 
by  steam  for  the  purposes  of  heating,  when  heat  is  to  be 
carried  to  some  distance  and  distributed.  The  mechani- 
cal work  necessary  to  "drive  steam  through  pipes  and 
radiators  "  exists  in  the  steam  itself,  for  its  inherent  prop- 
erty of  expansion  makes  it  self-driving. 

If  steam-pipes  could  be  perfectly  insulated,  so  as  ab- 
solutely to  prevent  exchange  of  temperature  between  them 
and  the  air,  heat  could  be  transferred  to  any  distance 
whatever,  and  without  loss.  Perfect  insulation  is  of  course 
impossible,  but  it  may  easily  be  made  sufficiently  good  to 
render  the  loss  in  a  single  large  building  practically 
nothing. 

This  has  been  demonstrated  by  Mr.  Holly,  who  has 
extended  the  system  from  heating  a  few  buildings  to  as 
many  hundreds,  where  the  steam  is  all  generated  in  one 
place  and  conveyed  through  carefully  insulated  tubes  to 
the  several  houses. 

The  method  of  insulating  the  pipes  which  Mr.  Holly 
used  maybe  described  in  the  words  of  his  circular  :  "The 
pipe  is  placed  in  a  lathe,  and  wound  about  first  with  as- 


134:  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

bestos,  followed  by  hair  felting,  porous  paper,  manilla 
paper,  finally  thin  strips  of  wood  laid  on  lengthwise,  and 
the  whole  fastened  together  by  a  copper  wire  wound  spi- 
rally over  all.  This  is  thrust  into  a  wooden  log,  bored  to 
leave  an  intervening  air-chamber  between  the  pipe  and 
the  wood,  and  of  sufficient  size  to  leave  from  three  to  five 
inches  of  wood  covering.  The  elasticity  of  the  wrappings 
permits  the  free  expansion  and  contraction  of  the  pipe 
irrespective  of  the  wooden  log,  which  is  securely  anchored 
and  made  immovable.  The  whole  is  placed  in  a  trench  a 
short  distance  below  the  surface  without  regard  to  frost. 
At  the  bottom  of  the  trench  is  laid  an  earthen  tile  drain 
to  carry  off  any  earth  moisture,  and  in  order  further  to 
insure  the  continuous  dryness  of  the  wooden  log  inclosing 
the  pipe."  , 

Such  careful  insulation  is  of  course  wholly  unnecessary 
in  the  heating  of  a  single  building.  This  description  is 
given  simply  as  an  example  in  further  demonstration  of 
the  principles  in  steam  heating. 

Mr.  Holly  also  demonstrated,  by  a  carefully  conducted 
experiment,  that  steam  may  be  conveyed  through  1,600 
feet  of  three-inch  pipe,  with  a  loss  by  radiation  of  only 
2%  per  cent.  This  is  sufficient  to  show  that  in  single 
buildings,  where  the  risers  are  about  the  only  pipes  from 
which  radiation  is  not  wanted,  the  loss  may  be  regarded 
as  practically  nothing. 

It  has  already  been  noticed  that  steam,  when  not  un- 
der pressure,  has  a  temperature  of  only  212°,  that  of  boil- 
ing water.  When,  however,  its  free  expansion  is  arrested, 
its  temperature  will  increase  in  proportion  to  the  pressure 
to  which  it  is  subjected.  It  is  better,  therefore,  in  order 
not  to  overheat  the  air  by  contact  with  superheated  iron, 
to  have  the  pressure  as  light  as  possible.  Here  is  another 
important  advantage  of  steam  heating  :  the  air  need  never 


STEAM  HEATING.  135 

be  overheated  if  a  proper  regulation  of  pressure  be  ob- 
served, and  a  sufficient  amount  of  piping  be  used  to  fur- 
nish the  requisite  surface  for  radiation. 

Steam-pipes  can  be  carried  to  any  place  in  a  building 
where  heat  is  desired.  In  most  other  systems  of  heating 
the  heads  of  the  occupants  of  a  room  inevitably  occupy 
a  position  having  a  higher  temperature  than  that  of  the 
feet.  This  is  exactly  the  reverse  of  what  it  should  be. 
Nothing  is  more  subversive  of  good  circulation  than  cold 
feet.  On  the  other  hand,  if  the  feet  are  kept  warm,  good 
circulation  may  comfortably  be  maintained,  even  when 
other  parts  of  the  body  are  subjected  to  a  comparatively 
low  temperature. 

An  arrangement  of  steam-pipes  beneath  the  floor,  as 
hereafter  described,  would  settle  the  question  of  cold  feet, 
and  remove  the  necessity  of  so  high  a  temperature  in 
other  parts  of  the  room  as  is  commonly  maintained. 
There  remains  no  question,  then,  as  to  the  superior  fa- 
cilities of  steam  for  heat  distribution. 

Its  cost  may  be  figured  otherwise  than  from  the  above 
negative  consideration  of  the  loss.  The  latent  heat  of 
steam  is  960,  that  is,  it  requires  960  units  of  heat  to  con- 
vert one  pound  of  boiling  water  into  steam.  This  is 
really  the  amount  that  is  actually  realized  as  heat.  The 
hot  water,  when  first  condensed  in  the  pipes,  does  on  its 
return  impart  some  of  its  heat  to  the  room,  but  the  same 
amount  will  be  necessary  to  raise  it  again  to  the  boiling- 
point  in  the  boiler  before  it  can  again  be  utilized.  Theo- 
retically, one  pound  of  coal  will  furnish  heat  sufficient  to 
convert  14  pounds  of  water  into  steam,  but  in  the  average 
practice  only  9  pounds  are  realized.  Then  960  X  9  = 
8,640  is  the  number  of  thermal  units  which  can  be  real- 
ized from  one  pound  of  coal. 

It  was  found,  when  calculating  the  cost  of  heating  in 


136  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

another  place,  that  142,959  units  of  heat  are  necessary  to 
supply  the  requirements  of  one  average  school-room  for 
one  hour,  where  all  the  demands  of  warming  and  venti- 
lating are  rigidly  complied  with.  Now,»142,959  -r-  8,640 
=  16  "66,  the  number  of  pounds  of  coal  necessary  to  sup- 
ply one  room  for  one  hour.  In  the  former  calculation  it 
was  found  that  18'3  pounds  was  the  number  required, 
which  shows  nearly  2  pounds  per  hour  in  favor  of  steam. 

So  far,  steam  has  been  treated  with  sole  reference  to 
its  warming  and  distributing  facilities.  Objection  is 
sometimes  made  to  steam  heating  that  it  does  not  furnish 
sufficient  ventilation.  To  this  it  may  be  answered  that 
the  same  is  true  of  any  method  of  heating  simply  as 
such 

It  has  already  been  explained  how  heating  and  venti- 
lating are  antagonistic  processes,  ventilation  always  being 
at  the  expense  of  heat.  In  any  method  of  heating  venti- 
lation must  be  provided  for  and  arranged  as  an  accessory 
to  the  heating.  No  heating  apparatus  is  in  itself  a  venti- 
lator. Good  ventilation  is  possible  with  any  system  of 
heating,  as  no  ventilation  at  all  frequently  accompanies 
good  methods  of  heating  when  by  themselves  considered. 

That  poorly  ventilated  school-houses  are  sometimes 
heated  by  steam  is  no  argument  against  steam  as  a  method 
of  warming ;  nor  does  it  prove  that  good  ventilation  is 
not  possible  with  steam  heating.  This  will  soon  be  made 
apparent  in  the  consideration  of  the  different  methods  of 
steam  heating,  which  are  of  three  kinds,  viz.,  heating  by 
direct  radiation,  by  indirect  radiation,  and  by  direct- 
indirect  radiation.  Heating  with  hot  water  is  not  well 
adapted  to  school-buildings,  which  are  occupied  only  at 
intervals.  This  .method,  therefore,  while  possessing  su- 
perior advantages  for  warming  private  dwellings,  will  not 
be  here  considered. 


STEAM   HEATING.  137 

Direct  Radiation. — In  direct  radiation  the  coils  of 
steam-pipe  or  radiators  are  placed  within  the  room  to  be 
warmed.  They  warm  the  air  of  the  room  by  radiation 
and  convection,  and  do  precisely  the  work  of  a  simple 
stove  where  heating  is  alone  provided  for  and  ventilation 
ignored.  The  single  point  of  superiority  of  this  method 
over  that  of  the  stove  is  in  the  comparatively  large  radi- 
ating surface  and  moderate  temperature.  As  a  mere 
heater,  where  the  temperature  of  the  room  is  alone  con- 
sidered, no  method  is  more  effective,  but  when  so  used  to 
the  neglect  of  ventilation,  heating  by  direct  radiation 
alone  can  not  be  too  heartily  condemned. 

Enough  has  already  been  said  concerning  the  evils  of 
heating  the  air  of  a  room  without  provision  being  made 
for  frequently  changing  it.  It  needs  only  to  be  noted 
here  that  nothing  is  more  certain  to  produce  these  evils 
than  direct  radiation  when  used  alone. 

This  must  not  be  considered  as  an  argument  against 
direct  radiation  in  itself,  but  by  itself  ;  indeed,  it  should 
form  a  part  of  every  system  of  steam  heating.  It  is  here 
condemned  only  when  used  exclusively.  When  direct  ra- 
diation is  used  in  association  with  a  good  aspirating  chim- 
ney, in  which  coils  of  steam-pipe  may  be  placed  to  give  a 
good  draft,  and  when  the  radiators  are  so  arranged  that 
the  cold  air  from  the  inlets  will  come  in  around  them  and 
be  warmed  before  reaching  the  occupants  of  the  room,  it 
makes  a  fairly  good  arrangement.  This  is  illustrated  in 
Fig.  21,  where  D  is  the  outside  wall ;  W,  the  window  ; 
E,  the  cold-air  duct ;  K,  the  radiator  ;  A,  the  ventilating 
shaft ;  B,  the  upper  foul-air  vent ;  C,  the  lower  foul-air 
vent.  The  arrows  show  the  direction  of  the  currents. 

This  arrangement  is  commonly  met  with  in  school- 
houses,  and  is  somewhat  better  than  no  provision  at  all 
for  ventilation,  but  it  is  very  inadequate.  The  heat  can 


138  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

not  by  this  means  be  properly  distributed.     If  the  outlet 
B  is  kept  open,  the  warm  unused  air  will  escape  ;  if  it  is 


FIG.  21. 


kept  closed,  the  foul  air  will  accumulate  in  the  top  of  the 
room.  The  radiator  K,  while  good  so  far  as  it  goes,  does 
not  warm  the  air  sufficiently  as  it  enters  to  prevent  cold 
drafts,  providing  the  inlets  are  sufficiently  large  for  the 
demands  of  ventilation. 

Steam  heating  by  direct  radiation,  even  without  any 
provision  for  ventilation  other  than  by  windows,  is  preva- 
lent, almost  discouragingly  so.  As  a  single  illustration, 
the  following  words  of  John  D.  Philbrick,  in  his  circular 
on  "  City  School  Systems  in  the  United  States,"  may  be 
used.  In  speaking  of  the  high-school  in  the  city  of  "Wash- 
ington he  says  :  "  It  is  to  be  regretted  that  the  high-school 


STEAM  HEATING.  139 

house  recently  erected  in  our  national  capital  should  be 
in  its  planning  so  far  behind  the  times.  Its  conspicuous 
absence  of  merit  was  not  to  have  been  anticipated,  consid- 
ering the  high  reputation  which  the  city  had  acquired  for 
good  school-house  building  in  the  erection  of  the  Frank- 
lin and  so  many  other  good  school  buildings.  .  .  .  The 
heating  is  effected  by  means  of  direct  steam  radiation." 

Washington  is  here  named  because  of  its  prominence 
and  the  common  interests  which  center  there  ;  but  it  is 
not  the  only  city  in  which  blunders  have  been  made,  and 
are  being  made,  in  school-house  building  relative  to  heat- 
ing and  ventilating.  In  fact,  the  taking  of  Washington 
as  typical  is  exceeding  liberality  toward  other  cities,  some 
of  which  are  really  much  worse. 

During  the  summer  of  1886  I  visited  many  school- 
buildings,  with  a  view  of  studying  their  provisions  for 
warming  and  ventilating.  Among  those  which  were 
warmed  by  direct  radiation,  several  were  arranged  as  rep- 
resented in  Fig.  22,  which  is  here  given,  as  some  of  these 
buildings  were  new  and  may  be  supposed  to  represent  the 
best  that  has  been  done  in  the  localities  where  they  were 
found.  The  figure  shows  the  interior  of  a  school-room 
with  the  two  sides  nearest  the  observer  removed.  R  rep- 
resents the  steam-pipes,  extending  along  the  sides  of  the 
room  under  the  windows.  S  is  a  ventilating  shaft  in  the 
corner  of  the  room  opposite  the  windows,  made  tight  at 
the  bottom,  with  no  provision  for  heating  the  air  inside 
of  it.  V  is  an  outlet  about  one  foot  square,  from  the 
room  into  the  ventilating  shaft,  and  situated  near  the 
floor.  No  provision  is  made  for  air  to  enter  the  room  ex- 
cept through  the  windows. 

The  theory  of  this  arrangement  is  difficult  to  guess, 
but  the  only  one  which  approaches  rationality  is  that  the 
air  is  expected  to  rise  from  the  pipes,  move  along  the  top 


140  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

of  the  room  to  the  opposite  corner,  then  to  dive  down  to 
the  bottom  of  the  room  and  crawl  up  the  shaft.     This, 

FIG.  22. 


while  quite  as  reasonable  as  many  current  ideas  concern- 
ing ventilation,  is  expecting  altogether  too  much  of  the 
air,  whose  power  of  moving  is  passive  and  not  active. 

The  air  will  rise  from  the  pipes  to  the  top  of  the  room. 
This  is  the  only  correct  supposition  in  the  above  supposed 
theory.  There  is  nothing  to  make  it  descend  when  it 
reaches  the  corner  opposite,  unless  it  is  colder  than  the 
air  below  it,  and  what  is  to  make  it  colder  ?  It  may  be 
at  a  temperature  lower  than  when  it  started  from  the 
pipes,  but  it  is  still  of  a  higher  temperature  than  the  air 
below  it,  in  all  parts  not  directly  over  the  pipes.  Hot  air 
constantly  rising  to  the  top  of  an  inclosed  space  will 
stratify  along  the  highest  plane,  the  warmest  occupying 
the  highest  level.  As  the  process  continues  the  line  of 


STEAM   EEATING.  141 

demarkation  between  warm  and  cold  air  will  descend 
lower  and  lower  till  the  floor  is  reached,  provided  there  is 
no  outlet  higher  than  the  floor  through  which  the  warm 
air  may  escape.  But  in  the  present  case  there  is  such  an 
opening,  for  the  air  is  expected  to  enter  at  the  windows, 
and  where  air  can  flow  in  when  room  is  made  for  it  within, 
it  can  also  flow  out  when  room  is  made  for  it  without. 
Now,  room  will  always  be  made  for  it  without,  when  the 
windows  are  on  the  leeward  side  of  the  room.  It  has 
been  previously  explained  how  wind  produces  a  partial 
vacuum  on  the  leeward  side  of  buildings  or  other  obstruc- 
tions. The  air  inside  will,  therefore,  have  a  tendency  to 
flow  outward  on  that  side  unless  there  is  some  counter- 
acting force  inside  to  prevent  it,  and  in  the  present  case 
there  is  none.  Cross-currents  will  thus  set  in,  and  the 
windows  will  be  both  inlets  and  outlets. 

If  this  little  foul-air  shaft  were  converted  into  an  as- 
pirating chimney  of  sufficient  size  in  which  heat  could  be 
easily  supplied  from  coils  of  steam-pipe  extended  into  it, 
there  would  be  something  to  counteract  this  influence  of 
the  wind,  as  well  as  to  furnish  an  adequate  exit  for  foul 
air.  In  short,  these  little  foul-air  shafts,  when  so  ar- 
ranged, are  almost  useless.  They  are  not  quite  useless, 
because  in  cold  weather,  when  the  air  is  still,  there  will 
be  a  slight  upward  draft  through  them,  due  to  the  air  in 
them  being  a  little  warmer  than  the  outside  air,  but  when 
the  wind  is  blowing  they  are  liable  to  become  inlets.  Di- 
rect radiation,  with  no  other  means  than  this  for  venti- 
lating or  preventing  cold  drafts,  is  objectionable.  The 
use  of  direct  radiation,  when  accompanied  with  other  pro- 
visions, will  appear  hereafter. 

Indirect  Radiation. — In  indirect  radiation  the  pipes 
are  not  placed  inside  of  the  room  to  be  warmed,  but  out- 
side in  an  inclosed  chamber  opening  into  the  room  and 


142  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

into  the  outside  air.  The  air  in  these  chambers  becomes 
heated,  rises  and  passes  into  the  room,  and  is  followed 
by  fresh  cold  air  from  outside  the  building. 

It  is  evident  that  a  room  warmed  in  this  manner  is  neces- 
sarily partially  ventilated,  for  the  warming  is  not  by  ra- 
diation or  convection,  but  from  inflowing  warm  air,  which 


FIG.  23. 


must  in  entering  displace  an  equal  amount  of  air  pre- 
viously in  the  room. 

This  method  of  warming  may  be  understood  by  ref- 
erence to  Fig.  23,  where  a  =  outside  wall  of  the  house  ; 
B  =  the  fresh-air  duct ;  c  the  register  opening  into  the 
room,  and  E  the  coils  of  steam-pipe. 


STEAM   HEATING.  143 

Indirect  radiation  should  be  accompanied  with  ade- 
quate means  for  abstracting  the  foul  air  from  the  room, 
either  in.  the  form  of  a  good  aspirating  chimney  or  a  ven- 
tilating fan.  Unless  this  be  done,  any  form  of  indirect 
radiation  will  fail ;  for,  as  two  bodies  can  not  occupy  the 
same  space  at  the  same  time,  the  foul  air  must  pass  out 
before  fresh  air  can  pass  in.  A  mere  outlet  into  the  open 
air  will  not  generally  suffice,  for  then  the  air  must  be 
pushed  out  by  the  air  coming  in  from  the  radiators,  a 
work  which  can  not  thus  be  adequately  performed. 

The  position  of  the  radiators  in  a  system  of  indirect 
radiation  may  vary  according  to  local  circumstances. 
Some  builders,  however,  have  a  rule  of  placing  them  in 
the  outside  walls,  and  others  in  the  inside  walls  near  a 
central  fresh-air  shaft  situated  near  the  center  of  the 
building.  Mr.  Baldwin  is  of  the  former  class,  and  gives 
as  a  reason  for  the  outside  position  that,  as  the  windows 
furnish  a  constant  source  of  rapid  cooling,  a  current  of 
cold  air  is  always  passing  down  inside  the  room  in  front 
of  them,  thence  along  the  floor,  cooling  the  feet  of  the 
occupants.  Placing  the  radiators  in  the  outside  walls 
under  the  windows  furnishes  an  upward  current  of  warm 
air  which  meets  this  cold  current,  thus  counteracting  it. 

Mr.  Briggs,  on  the  other  hand,  is  of  the  latter  class, 
and  gives  as  reasons  for  interior  locations  of  radia- 
tors :  That  basement  piping  is  thereby  saved ;  that  it 
obviates  danger  from  freezing  of  pipes  ;  that  it  prevents 
loss  of  heat  from  introduction  ducts  or  flues  which  run 
up  the  outer  exposed  walls  of  the  building,  and  that  the 
internal  location  makes  it  possible  to  place  the  inlets  and 
outlets  on  the  same  side  of  the  room,  which  it  is  claimed 
facilitates  the  bringing  down  of  the  warmed  air  from  the 
top  of  the  room,  where  it  first  rises,  to  the  breathing  line. 

Each  of  these  plans  of  locating  radiators  possesses 
14 


144  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

some  advantages  over  the  other,  but  both  are  equally  at 
fault  on  the  one  thing  necessary  to  make  steam  heating 
perfectly  successful.  Both  admit  the  warm  air  through 
a  few  large  openings  situated,  at  the  sides  of  the  room, 
where  it  at  once  rises  to  the  top  before  it  is  utilized. 
This,  of  course,  necessitates  the  placing  of  the  outlets 
near  the  floor,  in  order  to  retain  the  warm  air  till  it  has 
cooled  sufficiently  to  descend  and  be  used.  The  problem 
of  distributing  the  warm  air  as  it  enters  is  not  solved  by 
either  of  these  methods.  Until  it  is  solved,  until  the  air 
can  be  so  admitted  that  it  can  be  utilized  while  on  its 
way  to  the  top  of  the  room,  so  that  when  arriving  there 
it  may  be  let  out  at  the  ceiling,  the  place  where  Nature 
plainly  dictates  that  its  exit  should  be  made,  instead  of 
trying  to  force  hot  air  downward  ;  until  this  can  be  ac- 
complished, steam  heating  has  little  advantage  in  point 
of  ventilation  over  some  other  systems. 


CHAPTER  XIX. 

AN  IDEAL  PLAN"  FOB  WARMING   AND   VENTILATINQ. 

THE  necessary  physical  conditions  of  warming  and 
ventilating  have  now  been  fairly  well  discussed.  In  our 
investigations  of  the  different  plans  which  have  been  em- 
ployed, the  merits  and  demerits  of  each  have  been  pointed 
out.  While  all  have  some  characteristic  points  of  excel- 
lence, none  so  far  considered  are  without  numerous  and 
serious  defects.  Thus  far  no  system  has  been  devised 
that  so  distributes  the  air  as  it  enters  the  room  that  it 
may  be  let  out  at  the  top — the  place  which  Nature  plainly 
dictates  for  its  exit.  No  plan  has  yet  been  hit  upon  which 


AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING.    145 

keeps  the  feet  of  the  occupants  warmer  than  the  head — 
a  necessity  which  the  laws  of  blood-circulation  make 
plainly  evident.  No  system  has  yet  been  put  in  practice 
which  does  not  at  some  point  oppose  the  natural  laws  of 
ascent  and  descent. 

A  device  will  now  be  described  which  I  believe  will 
not  only  remedy  these  defects  but  will  comply  with  all 
the  requirements  of  ventilation.  In  order  better  to  esti- 
mate its  value,  let  us  first  enumerate  the  requirements 
of  ventilation.  1.  The  air  must  come  from  a  pure  source. 
2.  It  must  be  sufficient  in  quantity.  3.  It  must  be 
warmed  before  being  admitted  into  the  room.  4.  It 
must  not  be  overheated.  5.  It  must  be  distributed  as  it 
enters,  so  that  it  may  be  utilized  before  it  reaches  the  top 
of  the  room.  6.  In  order  that  this  may  be  possible,  it 
must  be  admitted  through  the  floor.  7.  It  must  not  be 
entrapped  in  the  top  of  the  room.  8.  The  ventilation 
and  air-supply  must  be  independent  of  doors  and  win- 
dows. 

A  careful  study  of  the  following  figures  will  show  how 
this  may  be  accomplished.  Fig.  24  shows  the  interior  of 
a  double  chimney,  with  partition  and  side  toward  the  ob- 
server removed  so  as  to  reveal  the  parts.  B  is  the  floor 
of  a»fresh-air  shaft  which  constitutes  one  division  of  the 
chimney,  as  shown  by  the  broken  partition  wall  E  Gr. 
H  is  the  opening  into  the  large  tube  C,  which  carries 
fresh  air  to  the  rooms  ;  X  X  shows  the  front  of  this  tube, 
cut  away  so  as  to  show  the  other  side.  J  J  are  floor- 
joists.  A  shows  where  the  fresh-air  tube  sends  off  a 
branch  directly  under  the  floor  of  the  first  story ;  F  is 
the  foul-air  register,  opening  from  the  top  of  the  room 
into  the  chimney.  J'  J'  A'  and  F'  show  corresponding 
parts  for  the  second  story.  A  is  the  floor  of  the  aspirating 
chimney,  which  contains  the  fresh-air  tube  just  described, 
7 


146  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING. 

and  also  the  smoke  pipes,  P,  which  come  from  the  fur- 
nace and  extend  to  the  top  of  the  chimney. 

The  action  of  this  chimney  explained  is  as  follows : 
This  chimney  is  to  perform  the  work  of  ventilating  and 
carrying  the  fresh  air  to  four  school-rooms.  The  large 
furnace  pipe  is  divided  into  the  several  smoke  pipes,  P, 
so  that  the  waste  heat  from  the  fire  may  be  utilized  in 
heating  the  air  in  the  chimney,  by  making  the  heated 
radiating  surface  as  large  as  possible.  The  air  in  this 
part  of  the  chimney,  thus  heated,  rapidly  rises  and  creates 
a  powerful  upward  draft,  making  a  partial  vacuum,  which 
draws  the  foul  air  through  the  foul-air  registers  F  at  the 
top  of  the  room.  The  smoke-pipes  arc  extended  upward 
to  the  top  of  the  chimney,  to  prevent  the  possible  reflux 
of  smoke  which  might  otherwise  occur  in  windy  weather. 
The  heat  from  these  pipes  will  also  be  communicated  to 
the  fresh-air  pipe  C  ;  and  the  fresh  air  which  it  contains, 
being  thus  warmed,  will  rise  and  pass  under  the  floor 
through  the  branch  tubes  A  and  A'.  It  would  probably 
be  better  to  have  the  fresh-air  tubes  leading  to  the  sepa- 
rate rooms  independent  of  one  another  to  avoid  inequality 
of  draft.  In  the  figure  two  rooms  are  represented  as  be- 
ing supplied  from  one  main  pipe  C,  merely  for  conve- 
nience of  illustration.  The  air  thus  rising  in  the  tube  C 
is  followed  by  cold  pure  air  from  the  fresh-air  shaft  B 
through  the  aperture  II.  This  shaft,  being  a  part  of  the 
chimney,  extends  to  the  top  of  the  building,  and  there- 
fore brings  the  air  from  an  elevated  and  pure  source. 
The  top  of  the  fresh-air  shaft  should  be  several  feet  be- 
low the  top  of  the  smoke  part  of  the  chimney  to  avoid 
the  drawing  down  of  smoke. 

As  we  have  seen  in  previous  pages,  this  chimney  must 
be  large.  There  is  little  danger,  under  the  present  ar- 
rangement of  conveying  the  smoke,  of  getting  it  too  large. 


VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


It  should,  if  built  for  four  rooms,  have  an  area  of  cross- 
section  of  at  least  64  square  feet,  making  it  equivalent  to 
8  feet  square.  Summarized,  a.  chimney  thus  constructed 
furnishes  an  outlet  for  smoke,  for  foul  air,  and  an  inlet 
for  fresh  air.  The  heat  in  it  from  the  furnace  has  a  ten- 
dency both  to  draw  the  foul  air  out  and  the  pure  air  into 
the  rooms,  as  explained. 

How,  now,  is  the  fresh  air  thus  admitted  beneath  the 
floor  to  be  warmed  and  distributed  ?  This  may  be  un- 
derstood by  reference  to  Fig.  25.  J  represents  a  series  of 

FIG.  25. 


floor  joists,  and  J'  another  series  resting  upon  the  first  at 
right  angles.    This  double  arrangement  is  to  give  sufficient 


AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING.     149 

room  for  the  various  radiating  boxes  necessary  to  perfect 
distribution.  The  inlet  a  corresponds  to  A  and  A'  of  Fig. 
24,  and  is  the  opening  into  the  box  B,  extending  along 
under  one  side  of  the  room  ;  0  are  openings  or  registers, 
opening  from  the  large  box  B  into  smaller  radiating  boxes 
b,  which  extend  along  under  the  floor  between  the  upper 
set  of  floor-joists  ;  s  s  are  steam-pipes  for  further  warm- 
ing the  air  as  it  enters. 

The  heat  from  this  source  gives  to  the  air  already  in 
motion  another  impulse  in  the  same  direction,  upward 
through  the  floor  register  R,  as  indicated  by  the  arrows, 
thus  further  increasing  and  securing  constancy  and  steadi- 
ness of  the  air  movement. 

The  air,  on  thus  entering,  will  be  properly  warmed, 
and  being  admitted  at  the  floor  will  secure  comfort  for 
the  feet.  There  should  be  a  radiating  box,  b,  for  every 
row  of  desks,  to  deliver  the  air  through  registers  situated 
at  frequent  intervals  along  the  aisles.  The  warm  air,  thus 
perfectly  distributed,  as  it  enters  rises  toward  the  ceiling, 
both  by  its  own  specific  lightness  due  to  temperature,  and 
by  its  tendency  to  fill  the  vacuum  produced  at  the  top  of 
the  room  from  the  draft  of  the  aspirating  chimney,  as 
explained  in  Fig.  24. 

Here  there  can  be  no  uncertainty  about  the  disposition 
of  C02  and  the  organic  emanations  from  skin  and  lungs. 
All  of  these  impurities  are  carried  off  as  fast  as  formed, 
both  from  a  tendency  which  an  animal  temperature  of 
98°  gives  them  to  rise,  and  the  constant  stream  of  rising 
air  into  which  they  are  poured. 

Steam-pipes  should  also  be  placed  in  the  large  radiat- 
ing box  B,  to  aid  both  in  warming  the  air  and  in  increas- 
ing the  strength  and  steadiness  of  the  movement.  These 
boxes  should  be  made  of  wood  and  lined  with  tin.  F  is 
the  floor  of  the  room.  At  0  there  should  be  a  damper 


150  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


for  regulating  the  draft,  and  controlled  by  a  lever  ex- 
tending up  through  the  floor.  The  opening,  a,  should 
be  large,  as  the  amount  of  air  delivered  through  it  is 
great.  The  form  and  proportion  are  of  course  not  speci- 
fied in  the  figure,  which  is  only  intended  to  make  the 
principle  of  the  movement  understood. 

What,  now,  it  may  be  asked,  will  prevent  the  space 
beneath  the  floor  from  filling  with  dirt  through  the  floor 
registers  ?  This  is  answered  in  Fig.  26,  which  represents 

FIG.  26. 


\J 

d  i 


d   *  d  t    d.   ,d 


a  cross-section  through  a  portion  of  the  floor,  the  radiat- 
ing box,  and  containing  steam -pipes.  F  shows  the 
floor  ;  r  the  connecting  box-riser  ;  b  b,  the  radiating  box  ; 
s  s  s,  the  steam-pipes  ;  and  II,  the  lid  of  the  register  in 
the  space  fitted  for  it  in  the  floor. 

The  peculiar  shape  of  this  lid,  as  represented,  will  be 
sufficient  to  suggest  how  the  dirt  is  prevented  from  fall- 
ing into  the  box.  Everything  which  falls  through  the 
spaces  at  the  top  of  the  lid  will  be  received  by  the  loops 
at  d.  The  arrows  indicate  the  direction  of  the  air  through 
the  numerous  holes  made  in  the  perpendicular  sides  of 
the  several  loops.  Floating  dust  will  have  no  tendency 
to  enter  these  holes,  because  the  current  of  air  will  pre- 


AN  IDEAL  FLAN  FOR  WARMING  AND  VENTILATING.     151 

vent  it,  being  from  the  direction  to  drive  it  away.  These 
lids,  made  of  light  castings,  will  not  be  expensive,  and 
can  be  easily  raised  out  and  freed  from  dirt,  which  from 
time  to  time  will  accumulate  in  the  loops. 

The  two  sets  of  floor-joists  which  this  system  necessi- 
tates will  incur  some  additional  expense,  but  this  will  be 
slight  when  the  accompanying  advantages  are  considered. 
The  greater  space  which  the  double  arrangement  would 
require  would  not  necessitate  any  increase  in  the  height 
of  the  building,  for  it  is  plain  that  when  rooms  are  venti- 
lated as  above  described,  the  height  of  the  room  is  not 
important.  The  number  of  cubic  feet  of  air  space  for 
each  pupil  loses  importance  as  perfect  ventilation  is  ap- 
proximated. Thousands  of  people  may  stand  crowded 
together  in  the  open  air  and  all  be  provided  with  pure 
air.  This  is  simply  because  the  ventilation  of  Nature  is 
perfect.  The  heated  emanations  from  the  body  rise  and 
fresh  air  comes  in  from  all  sides  to  fill  the  partial  vacuum. 
This  is  the  method  above  proposed.  The  movement  of 
all  the  air  in  the  room  is  upward,  with  ample  provision 
for  the  supply  of  plenty  of  fresh  warm  air  from  below. 

Thus  far  we  have  considered  ventilation  with  reference 
to  the  requirements  of  winter,  or  when  artificial  heat  is 
required  to  raise  the  internal  temperature  of  the  rooms 
above  that  of  the  outside.  In  the  fall  and  spring,  when 
no  extra  heat  is  needed  in  the  rooms — when  the  internal 
and  external  temperatures  are  nearly  equal — it  is  then 
only  necessary  to  heat  the  air  in  the  foul-air  compartment 
of  the  chimney  in  order  to  maintain  a  draft  sufficient  to 
abstract  the  foul  air  as  fast  as  formed.  There  are  several 
ways  to  do  this.  A  stove  may  be  set  at  the  bottom  of  the 
chimney,  or  coils  of  steam-pipe  may  extend  into  it  from 
the  boiler.  For  the  system  we  are  considering  this  is  the 
proper  method  of  heating  the  chimney  in  warm  weather. 


152  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

By  means  of  valves  the  steam  may  be  shut  off  from  all 
the  radiator  pipes,  allowing  it  to  pass  only  through  the 
pipes  in  the  chimney.  And,  owing  to  the  manner  in 
which  the  heat  of  the  smoke  and  the  waste  products  of 
combustion  are  utilized,  the  necessary  heat  could  be  by 
this  means  most  economically  produced. 

This  heating  of  the  chimney  in  warm  weather  should 
not  be  neglected.  It  is  commonly  supposed  that  in  warm 
weather,  when  the  windows  may  be  opened,  ventilation  is 
easily  secured.  This  is  a  great  mistake.  It  is  easier  to 
ventilate  in  winter  than  in  summer.  In  cold  weather  the 
inequality  of  internal  and  external  temperature  is  in  itself 
a  cause  of  movement,  as  heretofore  explained  ;  but  when 
the  internal  and  external  temperatures  are  nearly  equal, 
change  of  position  takes  place  (in  the  absence  of  wind) 
only  by  diffusion. 

In  order  to  suit  the  conditions  of  cool  weather,  when 
a  little  heat  is  needed,  the  pipes  extending  through  the  ra- 
diators should  be  connected  in  sections,  so  that  steam 
could  be  shut  off  from  any  number  of  them  as  desired. 
For  instance,  Fig.  27  shows  a  main  supply  pipe,  sending 
off  branches  which  are  again  subdivided,  each  sending  a 
pipe  to  the  several  radiators.  Thus,  section  A  sends  one 
pipe  through  each  radiating  box  in  the  building ;  section 
B  another,  section  C  another.  When  only  a  third  of  the 
usual  amount  of  heat  is  required,  all  the  valves  are  closed 
except  C,  through  which  steam  will  then  alone  be  admit- 
ted. If  more  heat  is  needed,  open  valve  B.  In  coldest 
weather,  open  all.  For  the  severest  weather,  in  high  lati- 
tudes, a  section  should  be  set  apart  leading  to  direct  ra- 
diators placed  in  the  rooms.  By  skillful  management  of 
the  details  any  temperature  may  be  secured  and  ventila- 
tion be  equally  good  in  all  seasons. 

Another  advantage  which  the  double  set  of  floor-joists 


AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING.    153 


secures  is  in   the  effectual  deadening  of  sound  which 
the  enlarged  space  would  secure.     In  all  school-houses  of 


FIG.  27. 


B 


B' 


C' 


RADIATOR  BOX 


two  or  more  stories  some  means  of  deadening  the  sound 
of  moving  feet,  conducted  through  the  floor  and  ceiling 


154  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

to  the  room  below,  is  absolutely  essential.  Where  this  is 
effectually  done,  the  cost  will  exceed  that  of  the  double 
joists.  This  system  of  warming  and  ventilating,  it  ap- 
pears to  me,  answers  all  the  requirements  of  ventilation  : 
1.  The  air  taken  from  the  height  of  the  building  is  from 
a  pure  source.  2.  From  the  large  size  of  the  chimney 
and  fresh-air  shaft,  this  air  is  sufficient  in  quantity.  3. 
By  the  distribution  of  steam-pipes  as  described  it  is 
warmed  before  being  admitted  into  the  room.  4.  By  a 
proper  apportionment  of  these  pipes  the  air  need  not  be 
overheated.  5.  By  the  numerous  small  registers  distri- 
bution is  perfect.  6.  It  is  through  the  floor,  thus  secur- 
ing the  warmth  of  the  feet.  7.  It  is  not  entrapped  in  the 
upper  part  of  the  room,  but  rapidly  hurried  away  from 
this  point.  8.  The  inlets  and  outlets  being  of  ample  size, 
and  the  velocity  of  the  air  sufficient,  the  ventilation  will 
be  independent  of  doors  and  windows. 

On  the  latter  point  too  much  stress  can  not  be  laid. 
Open  doors  and  windows,  especially  in  a  city,  are  a  source 
of  great  annoyance.  The  rattle  of  passing  vehicles,  the 
din  of  machinery  and  steam- whistles,  sometimes  render  it 
impossible  to  hear  a  recitation.  In  windy  weather  great 
clouds  of  dust  from  the  streets,  and  smoke  from  neigh- 
boring chimneys,  pour  in  through  open  windows  to  com- 
plete the  discomfiture  of  all  helpless  victims  of  window 
ventilation.  In  winter,  where  windows  are  relied  upon, 
currents  of  icy  cold  air  pour  in,  endangering  the  lives  of 
pupils  ;  while  currents  of  warm  air  pour  out,  sometimes 
before  it  has  been  utilized. 

It  will  doubtless  be  a  surprise  to  many  that  the  fresh- 
air  shafts  and  chimneys  for  foul  air  need  to  be  so  large  ; 
but  a  careful  perusal  of  the  foregoing  pages  will  convince 
the  intelligent  reader  that  there  is  no  help  for  this  if  any- 
thing like  perfect  ventilation  is  approximated.  Facilities 


AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING.     155 

for  ventilation  are  to  a  house  what  lungs  are  to  an  ani- 
mal. They  must  be  capacious  and  active,  to  maintain  a 
healthy  and  vigorous  life.  The  ventilating  and  warming 
apparatus  constitute  the  vital  organs  of  a  building,  and 
are  therefore  of  first  importance  in  school-house  building. 
Utility  first  and  ornamental  finish  last.  Where  utility 
and  architectural  symmetry  conflict,  the  latter  should 
give  way  to  the  former.  Give  us  life  first  and  beauty 
second.  However,  it  need  not  be  supposed  that  sym- 
metry is  necessarily  sacrificed  or  school-room  capacity  in- 
terfered with  by  the  use  of  these  generous  chimneys. 

The  three  essential  qualities  of  a  school-house,  named 
in  the  order  of  their  importance,  are  utility,  simplicity, 
and  beauty.  If  these  qualities  are  attended  to  in  the  or- 
der here  named,  all  three  are  possible  of  attainment ;  but 
if  the  order  be  reversed,  as  is  commonly  the  case,  only 
the  first — beauty — will  be  attained. 

In  a  two-story  building  one  chimney  should  not  be 
required  to  serve  more  than  four  rooms.  If  three  stories, 
it  may  supply  six  rooms.  A  peculiarity  of  this  system  of 
ventilating  is  that  the  higher  the  building  the  greater  is 
its  efficiency.  The  reason  for  this  is  evident.  The  draft  of 
a  chimney  is  not  only  always  increased  with  its  height,  but 
in'this  case  the  higher  the  building  the  farther  the  fresh- 
air  tubes  will  extend  upward  through  the  heated  air  of  the 
aspirating  chimney.  This  not  only  adds  still  more  power 
to  the  draft,  by  the  additional  heat  given  to  the  ascending 
fresh  air,  but  this  heat  is  utilized  in  giving  additional 
warmth  to  the  air  before  it  enters  the  radiators. 

There  are  many  designs  which  might  be  made,  where- 
by all  the  qualities  of  a  good  school-house  are  secured. 
An  original  plan  is  suggested  in  Fig.  28,  which  may  be 
considered  the  first  story  either  of  a  two  or  three  story 
building.  If  two  stories,  there  will  be  sixteen  rooms  ;  if 
15 


156  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


• 



PORCH 

SCHOOL  ROOM 

|          1 

SCHOOL  ROOM 

1  1 

II 
CU.                 HATS 

1                                        1 

1 

HATS           CL.|B   A 

SCHOOL  ROOM 

-J 

SCHOOL  ROOM 

SIDE  ENTRANCE 

_J 
< 

X 

SIDE  ENTRANCE               §j 

SCHOOL  ROOM 

1 

SCHOOL  ROOM 

A      B  1  CL.                 HATS 

1                 1 

HATS            CL.IB   A 

™" 

L^P" 

SCHOOL  ROOM 
24'  X  34' 

.  "  . 

SCHOOL  ROOM 
24'  x  34' 

J             PORCH 

A.  foul  air  and  smoke. 

R                 , 

•  *res"'  Mr" 

AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING.    157 

three  stories,  twenty-four  rooms.  This  is  as  many  rooms 
as  will  commonly  be  found  necessary  in  a  single  building. 

The  plan  is  self-explanatory.  The  spaces  between  the 
rooms  serve  the  purposes  of  fresh  air,  foul  air,  smoke, 
water-closet,  and  hat-room.  The  water-closet  adjoins 
the  foul-air  part  of  the  chimney.  An  opening  through 
the  dividing  wall  will  effectually  ventilate  the  closet.  A 
is  the  smoke  and  foul-air  part  of  the  chimney,  and  B 
the  fresh-air  shaft ;  the  latter  communicating  with  the 
former,  as  shown  in  Fig.  24.  The  combined  chimney 
and  fresh-air  shaft  should  have  at  least  G4  square  feet 
sectional  area.  It  may  be  made  by  this  plan  of  almost 
any  size  without  inconvenience  or  sacrifice  of  symmetry. 
Iron  ladders  should  be  secured  on  the  inside  of  both  com- 
partments of  the  chimney  to  facilitate  the  adjustment  and 
repair  of  the  various  pipes. 

One  half  of  this  design  makes  a  plan  for  an  eight- 
room  building.  Eight  rooms  is  generally  preferable  to 
any  other  number.  For  this  arrangement  not  only  gives 
unobstructed  light  on  two  sides  of  each  room,  but  more 
easily  meets  architectural  requirements,  and  is  sufficient 
to  serve  the  ends  of  ordinary  graded  school-work.  The 
large  plan  is  here  given  to  answer  the  requirements  in 
large  and  crowded  cities  where  the  economy  of  space  re- 
quires as  few  buildings  as  possible,  and  for  high-school 
buildings  where  eight  rooms  are  sometimes  insufficient  to 
serve  the  demands  of  the  proper  specialization  of  the 
various  departments. 

Fig.  29  is  a  plan,  illustrating  how  the  same  qualities 
may  be  secured  in  a  building  of  6  or  12  rooms. 

The  advantages  which  these  plans  secure  are  :  1.  The 
whole  building  is  perfectly  warmed  and  ventilated.  2. 
There  is  light  on  two  sides  of  each  room.  3.  The  chim- 
neys are  out  of  the  way  and  do  not  project  into  the  school- 


158  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


rooms.  4.  There  is  plenty  of  blackboard  room  on  plane 
surface  unbroken  by  ad  jutting  chimneys  and  a  multi- 
plicity of  windows. 

Let  it  be  noted  here  that  narrow  hat-rooms  are  gen- 


Fia.  29. 


SCHOOL 
ROOM 


r-|A|B 
SCHOOL  ROOK  l 


SCHOOL 
ROOM 


-'SCHOOL  ROOM 


SCHOOL 
ROOM 


SCHOOL 
ROOM 


PORCH 


REFERENCE. 

A.  Foul  air  and  »7»oi<. 

B.  Fresh  air.. 


erally  a  nuisance,  and  a  source  of  crowding  and  disorder 
at  dismissal.  The  halls  should  be  wide,  with  a  stationary 
hat-rack  extending  along  each  side  about  three  feet  from 
the  wall.  This  arrangement  gives  not  only  plenty  of  room 
for  hats  and  wraps,  but  makes  them  accessible.  The  small 
hat-rooms  in  the  foregoing  plan  are  given  not  so  much  to 
meet  any  real  necessity  for  them,  as  to  utilize  space  which 


AN  IDEAL  PLAN  FOR  WARMING  AND  VENTILATING.     15Q 

would  otherwise  be  useless.  By  using  them  as  merely 
supplementary  to  the  hall  space,  crowding  in  them  may 
be  avoided. 

These,  it  appears  to  me,  are  some  of  the  essentials  of 
a  school-house.  I  leave  the  superficial  embellishments  to 
the  taste  of  the  architect.  Towers,  turrets,  buttresses, 
cantilevers,  balustrades,  consoles,  corbels,  scrolls,  cupolas, 
pilasters,  pendants,  paint,  and  colored  glass  are  of  later 
consideration.  These  are  all  useful  after  the  essentials 
are  first  secured.  They  are  educative,  and  should  be  en- 
couraged to  the  full  extent  of  the  remaining  means  for 
procuring  them  after  the  vital  organs  have  been  intelli- 
gently planned  and  skillfully  adjusted. 

NOTE. — A  patent  on  this  system  has  been  applied  for. 


APPENDIX. 


BY  a  long  and  laborious  series  of  observations  with 
hygrometers  and  dry-  and  wet-bulb  thermometers,  Mr. 
Glaisher  deduced  empirically  a  series  of  factors  which  are 
of  inestimable  value  in  testing  the  humidity  of  the  air  by 
means  of  the  wet  and  dry  bulbs.  To  use  these  factors, 
multiply  the  difference  between  the  dry  and  wet  bulb 
readings  by  the  factor  which  stands  opposite  the  dry  bulb 
temperature,  and  the  product  subtracted  from  the  dry 
bulb  temperature  will  give  the  dew  point. 

Let  t  =  temperature  of  dew  point. 

"  tz-  "          "dry  bulb. 

"  t1--  "          "wet  bulb. 

"  lc  =  factor. 
We  then  have  the  formula 

t  =  ?-(?-?)& (1.) 


APPENDIX  A. 
GLAISHER'S  FACTORS. 


101 


Reading 
of  dry 
bulb. 

Factor  *. 

Reading 
of  dry 
bulb. 

Factor  *. 

Reading 
of  dry 
bulb. 

Factor  *. 

Reading 
of  dry 
bulb. 

Factor*. 

10° 

8-78 

33° 

3-01 

66° 

1-94 

79° 

1-69 

11 

8-78 

34 

2-77 

57 

1-92 

80 

1-68 

12 

8-78 

35 

2-60 

58 

1  90 

81 

1-68 

13 

8-77 

36 

2-50 

59 

1-89 

82 

1-67 

14 

8-76 

37 

2-42 

60 

1-88 

83 

1-67 

15 

8-75 

38 

2-36 

61 

1-87 

84 

1-66 

16 

8-70 

39 

2-32 

62 

1-86 

85 

1-65 

17 

8-62 

40 

2-29 

63 

1-85 

86 

1-65 

18 

8-50 

41 

2-26 

64 

1-83 

87 

1-64 

19 

8-34 

42 

2-23 

65 

1-82 

88 

1-64 

20 

8-14 

43 

2-20 

66 

1-81 

89 

1-63 

21 

7-88 

44 

2-18 

67 

1-80 

90 

1-63 

22 

7-60 

45 

2-16 

68 

1-79 

91 

1-62 

23 

7-28 

46 

2-14 

69 

1-78 

92 

1'62 

24 

6-92 

47 

2-12 

70 

1-77 

93 

1-61 

25 

6-53 

48 

2-10 

71 

1-76 

94 

1-60 

26 

6-08 

49 

2-08 

72 

1-75 

95 

1-60 

27 

5-61 

50 

2-06 

73 

1-74. 

96 

1-69 

28 

5-12 

51 

2-04 

74 

1-73 

97 

1-59 

29 

4-63 

52 

2-02 

75 

1-72 

98 

1-58 

30 

4-15 

53 

2-00 

76 

1-71 

99 

1-58 

31 

3-66 

54 

1-98 

77 

1-70 

100 

1-57 

32 

3-32 

55 

1-96 

78 

1-69 

The  elastic  force  of  vapor  of  water  increases  with  the 
temperature.  If,  then,  the  elastic  force  of  vapor  of  water 
at  the  temperature  of  saturation  (dew  point)  be  divided 
by  the  elastic  force  of  'vapor  at  a  given  temperature,  the 
quotient  will  express  the  ratio  of  humidity  to  saturation. 
The  following  table  shows  the  elastic  force  of  vapor  of 
water,  measured  in  inches  of  mercury  : 
Let  t  =  temperature  of  dew  point. 

"  R  =  ratio  of  humidity. 

"  p  =  elastic  force  of  vapor  at  temperature  T. 

"  T  =  temperature  of  the  air. 

"  p'  =  elastic  force  of  vapor  at  temperature  I  (dew  point). 

=  £'.  (2.) 

P 


1G2  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 


Tempera- 
ture of 
the  air. 

v,-S*£' 

0  fe  S  g 
8  111 

S*£a 
S 

Tempera- 
ture of 
the  air. 

q^  £ 

III! 

z$aa 
i* 

Tempera- 
ture of 
the  air. 

«M-S°£ 

lill 

O    ^^3    0) 

s£«a 

IS 

N 

C.O   ~ 

SsS 

&"> 

Force  of 
vapor  in 
Inches  of 
mercury. 

T° 

/> 

yo 

p 

T° 

p 

T° 

P 

0 

0-044 

24 

0-129 

48 

0-335 

72 

0-785 

I 

0-046 

25 

0-135 

49 

0-348 

73 

0-812 

2 

0-048 

26 

0-141 

50 

0-361 

74 

0-840 

3 

0-050 

27 

0-147 

51 

0-374 

75 

0-868 

4 

0-052 

28 

0-153 

52 

0-388 

76 

0-887 

5 

0-054 

29 

0-160 

53 

0-403 

77 

0-927 

6 

0-057 

30 

0-167 

54 

0-418 

78 

0-958 

7 

0-060 

31 

0-174 

55 

0-433 

79 

0-990 

8 

0-062 

32 

0-181 

56 

0-449 

80 

1-023 

9 

0-065 

33 

0-188 

57 

0-465 

81 

1-057 

10 

0-068 

31 

0-196 

58 

0-482 

82 

1-092 

11 

0-071 

35 

0-204 

59 

0-500 

83 

1-128 

12 

0-074 

36 

0-212 

60 

0-518 

84 

1-165 

13 

0-078 

37 

0-220 

61 

0-537 

85 

1-203 

14 

0-082 

38 

0-229 

62 

0-556 

86 

1-242 

15 

0-086 

39 

0-238 

63 

0-576 

87 

1-2&2 

16 

0-090 

40 

0-247 

.64 

0-596 

88 

1-323 

17 

0-094 

.41 

0-257 

65 

0-617 

89 

1-566 

18 

0-098 

1     4? 

0-267 

66 

0-639 

90 

1-401 

19 

0-103 

43 

0-277 

67 

0-661 

91 

1-455 

20 

0-108 

44 

0-288 

68 

0-685 

92 

1-501 

21 

0-113 

45 

0-299 

69 

0-708 

93 

1-548 

22 

0-118 

46 

0-311 

70 

0-733 

23 

0-123 

47 

0-323 

71 

0-759 

Example  1. — Suppose  the  temperature  of  the  room  as 
indicated  by  the  dry  bulb  to  be  72°  ;  the  temperature  of 
the  wet  bulb  68°.  Kequired  the  temperature  of  the  dew 
point,  and  the  degree  of  humidity.  In  formula  (1)  t*  = 
72°  ;  t'  =  68°  ;  k  =  1'75  ;  then,  t  =  72°  -  (72°  -  68) 
1-75;  £  =  47-5°. 

In  formula  (2)  p',  for  47 '5°  =  0-323  ;  p,  for  72°  = 

0-785  :  K  =  -  =  .  „-.,  =  -40  (per  cent  of  saturation). 
p      0-785 

This  shows  an  atmosphere  somewhat  too  dry.  The  de- 
grees of  difference  between  the  dry  and  wet  bulb  readings 
which  should  exist  in  order  to  conform  to  any  required 
standard  may  be  shown  by  the  following: 


APPENDIX  B.  103 

Example  2. — If  the  temperature  of  the  room  as  shown 
by  the  dry-bulb  thermometer  be  72°,  what  should  be  the 
temperature  of  the  wet  bulb  in  order  to  conform  to  the 
provisional  standard  of  humidity  given  by  de  Chaumont, 
73°  ?  From  formula  (2)  p'  =  Up  -  -73  X  '785  =  '573. 
The  degree  in  the  table  corresponding  to  this  number  is 
63°.  This  is  the  dew  point  corresponding  to  our  standard. 

v                  i    ,iw/      t+t*lc-t*      63+(l -75X72)-  72 
From  formula  (1)  t  =  — ! — r =  —  v  — 

K  i.   <  u 

=  66,  the  number  of  degrees  which  should  be  shown  by 
the  wet  bulb  when  the  dry  bulb  shows  72°. 


B. 

Aspirating  chimneys  and  ventilating  shafts  are  some- 
times employed  to  counteract  the  force  of  the  wind,  to 
increase  the  velocity  of  the  flow  of  air  into  the  room  by 
means  of  a  fire  in  the  chimney,  to  warm  the  air  before  it 
enters  the  room,  and  to  draw  the  air  from  an  elevated 
source  to  insure  purity.  The  following,  Fig.  30,  illus- 
trates a  simple  form,  sufficiently  accurate  to  illustrate  the 
use  of  the  formulas,  though  not  ideally  correct  as  to  the 
relative  position  and  number  of  openings.  Reference  : 
1,  entrance  shaft ;  2,  horizontal  air-ducts ;  3,  room  ;  4, 
aspirating  chimney  ;  5,  grate.  We  have  here,  in  addition 
to  the  conditions  before  given,  an  acceleration  in  the  ve- 
locity of  the  air  entering  the  room  due  to  the  aspirating 
power  of  the  chimney  ;  increase  of  temperature  in  the 
chimney  by  fire  ;  and  friction  due  to  the  surfaces  and 
angles  in  the  air-passages.  The  co-efficients  of  friction 
used  by  engineers  are  as  follows  :  In  ducts,  0*024  ;  for 
rough  flues,  0*05  ;  for  brick  flues,  0*05  ;  for  square  elbow, 


164  VENTFLAflON  AND  WARMING  OF  SCHOOL-BUILDINGS. 

1'50  ;  for  circular  elbow,  0'50  ;  air  passing  from  a  larger 
to  a  smaller  flue,  '50  ;  air  passing  through  a  wall  or  plate, 


FIG.  30. 


0*50  ;  air  passing  from  a  smaller  to  a  larger  flue  through 
an  opening  in  the  wall,  Fig.  31.     Eeference  :  A,  A1,  A3 


FIG.  31. 


=  areas  of  flues  ;  /  =  co-efficient  of  friction  in  ducts  ; 
f1  =  co-efficient  of  friction  in  elbows ; 


APPENDIX  B.  165 

a  -  -60  when  A  >  A8,  /'  =  J  -^-  -  1  I*, 

when  A1  =  A8  <  A,  fl  =  j  A  ..  i  I*. 

When  the  angle  of  a  tube,  ventilating  shaft,  or  other  air- 
passage  is  not  90°  the  conditions  of  any  angle  between  0 
and  180°  may  be  approximately  expressed  by  the  formula  : 

1  -4-  cos  0 

— .     With  these  new  elements,  and  from  the  fact 
a 

that  the  velocity  is  inversely  proportional  to  the  square 
root  of  the  friction,  and  that  for  similar  cross-sections 
the  friction  is  inversely  as  the  diameter,  we  have  the 
following,  another  modification  of  Montgolfier's  for- 
mula : 


v  = 


+  et 


where  V  =  velocity  of  air  in  feet  per  second  in  ducts. 
e  =  expansion  of  air  for  1°  Fahr.,  '00203. 
t  =  external  temperature. 
12=  internal  temperature  of  the  chimney. 
I  =  length  of  ducts,  including  h  + 1?  +  Z1  +  Z2. 
f  =  co-efficient  of  friction  in  ducts. 
f1  =  co-efficient  of  friction  in  elbows. 
g  =  acceleration  due  to  gravity  =  32*166  feet. 
d  =  diameter  of  ducts. 
K1  =  height  of  aspirating  chimney. 
h?  =  height  of  entrance  chimney. 
h  =  total  height  of  chimneys. 

Example.— Suppose  that  &  =  100°  ;  t  =  60  ;  I  =  h  + 
A«  +  |>  +  ?  =  80  -f  30  +  8  +  8  =  126  feet ;  h  =  80  ;  /  = 
•05  for  brick  flues  ;  f1  for  2  square  elbows  =  1*5  X  2  =  3 ; 
d  =  3.  Then: 


166  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS 

0303  (loo  —  60) 

+1)0808x66- 


=  4/'00303  (loo  —  60)   2  x  aa-ie  x  so  _ 

7- 


,/-0812  X  5145-6  _     741^82272  _ 

"  riaiS  X  6-266  ~        T62  :V59-44  =  7'7  feet 


291         ^ 

per  second.  This,  being  the  rate  at  which  the  air  passes  out 
of  the  room,  may  also  be  taken  as  the  rate  passing  in.  It 
thus  appears  that  where  the  friction  is  considerable  the 
aspirating  chimney,  or  other  means  of  accelerating  the 
movement  of  air,  becomes  a  necessity. 


C.     (See  page  84.) 

The    following    formulas,  taken    from    Schumann's 
"  Manual,"  will  be  useful  in  determining  the  size  and 
construction  of  the  various  parts  of  the  fan  : 
Eeference  : 

V  =  volume  of  air  delivered  in  cubic  feet  per  second. 

h  =  height  of  manometer. 

c  =  velocity  of  air  entering  the  fan. 

O=.  velocity  of  air  leaving  the  fan. 

r  =  outer  radius  of  vanes. 

n=  inner  radius  of  vanes. 

ra=  radius  of  inlet. 

I  =  width  of  vanes. 

a  =  height  of  outlet. 

«t=  distance  from  vertical  radius  to  point  e  (see  Fig.  14). 

n  =  number  of  revolutions  per  minute. 

p  =  radius  of  a  circle  whose  diameter  is  unity  =  3 '141 6. 

/\T 
—  ,  where  there  is  one  inlet. 
cp 

/~^V~ 

rs=  i/  - — ,  where  there  are  two  inlets. 
2cp 


APPENDIX   D.  167 

r  2 
b  =  p.—  ,  where  there  is  one  inlet. 


« 

b  =  —  ,  where  there  are  two  inlets. 
r 

V 

b  =  5  -  ;  rt  =  r2  to  2  r8  ; 
2  j9  rt  c 

2636    /=-  V 

n  =  -  Vh  ;  a  —  j—  ; 
r  Jcj  ' 

«!=  0-159  a. 


D. 

CONDUCTING   POWEB  OF  MATEEIALS.    • 

Value  c,  being  the  units  of  heat  transmitted  per  hour 
per  square  foot  of  a  plate  1  inch  thick,  the  two  surfaces 
differing  in  temperature  1°. 

c  = 

Copper 515-000 

Iron 233-000 

Zinc 225-000 

Lead 113-000 

Marble,  gray,  fine  grained 28-000 

•   Marble,  white,  coarse  grained 22  -400 

Stone,  calcareous,  fine 16*700 

Stone,  calcareous,  ordinary 13-680 

Glass 6-600 

Brick-work,  baked  clay 4-830 

Plaster,  ordinary 3  -860 

Oak,  perpendicular  to  fibers 1  '700 

Walnut,  perpendicular  to  fibers 0-830 

Pine,  perpendicular  to  fibers 0-748 

Pine,  parallel  to  fibers 1-370 

Walnut,  parallel  to  fibers 1  '400 

16 


168  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

C  = 

Gutta-percha 1-380 

India-rubber 1  -370 

Brick-dust,  sifted 1  -330 

Coke,  pulverized 1  -290 

Cork 1-150 

Chalk,  in  powder 0*869 

Charcoal  of  wood,  powdered 0-636 

Straw,  chopped 0-563 

Coal,  small  sifted 0-547 

Wood-ashes  . . . , 0-531 

Mahogany  dust 0-523 

Canvas  of  hemp,  new 0-418 

Calico,  new 0-402 

Writing-paper,  white 0'346 

Cotton  or  sheep's  wool 0  -323 

Eider-down 0-314 

Blotting-paper,  gray 0-274 

For  double  windows,  when  the  glass  is  not  less  than  2 
inches  apart,  c  =  3  -6. 

Stagnant  air,  c  —  0  -3. 


E. 

Value  of  r,  being  the  radiating  and  absorbing  power 
of  bodies,  in  units  of  heat  per  square  foot,  for  a  difference 
of  1°  Fahr.,  from  the  experiments  of  Piclet : 

r  = 

Silver,  silvered  copper 0-02657 

Copper 0-03270 

Tin 0-04395 

Zinc  and  brass,  polished 0-04906 


APPENDIX  F.  169 


Iron,  tinned  ........................  0-08585 

Iron,  sheet  .........................  0-09200 

Iron,  ordinary  ____  .  ..................  0-56620 

Iron,  cast,  new  ......................  0*64800 

Iron,  sheet  and  cast,  rusted  ...........  0*68680 

Lead,  sheet  .........................  0-13286 

Glass  ..............................  0-59480 

Chalk  ..............................  0-67860 

Wood  sawdust,  fine  ..................  0-72150 

Building  stones,  plaster,  wood,  brick  ..  0-73580 
Sand,  fine  ..........................  0-74000 

Calico  ..............................  0-74610 

Woolen  stuffs  .......................  0-75220 

Silk  stuffs,  oil  paint  .................  0-75830 

Paper  ..............................  0-77060 

Lampblack  ................  .........  0-81960 

Water  ..............................  1-08530 

Oil.  .  1-48000 


F.     (See  page  87.) 

T7ie  Blackmail  Fan. — My  invention  is  a  ventilating- 
fan,  constructed,  as  fully  described  hereinafter,  so  as  to 
rapidly  transmit  motion  to  large  volumes  of  air,  carrying 
the  same  in  solid  columns  without  dispersing  it  or  creating 
back  currents. 

In  the  drawings,  Fig.  A  (see  page  87,  .Fig.  13)  is  a  near 
view  of  a  ventilating-fan  with  my  improvements.  Fig.  B 
is  a  section  on  the  line  1,  2,  Fig.  A.  Figs.  C  to  G  (Fig. 
32,  page  170)  are  diagrams  illustrating  the  formation  of 
the  blades.  Fig.  II,  a  perspective  view  of  a  blade  and  the 
hub.  • 


170  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 
\y  FIG.  32. 


ITig.D 


Fig.O 


o 


APPENDIX  F.  171 

In  experimenting  with  that  class  of  fans  used  to  ptit 
air  in  motion  for  ventilating  and  other  purposes,  I  ascer- 
tained that,  in  ordinary  constructions,  while  volumes  of  air 
would  be  driven  forward  by  the  revolution  of  the  fans,  other 
volumes  would  be  thrown  off  radially,  and  still  others 
would  be  thrown  backward  instead  of  forward,  as  desired, 
creating  currents  interfering  with  the  free  flow  of  air  to 
the  fan.  After  many  experiments  I  ascertained  that  by 
bending  each  blade  outward  at  the  upper  end,  forming  per- 
ipheral sections,  thus  compelling  the  large  volumes  ordi- 
narily dissipated  in  this  direction  to  move  directly  forward. 

My  present  invention  relates  to  certain  improvements 
whereby  I  have  succeeded  in  preventing  altogether  any 
back-flow,  insuring  a  forward  propulsion  of  all  the  air 
coming  within  the  influence  of  the  wheel. 

In  the  course  of  my  experiments  I  ascertained  that  it 
was  necessary  to  so  construct  each  blade  of  the  wheel  as 
to  draw  or  deflect  outward  the  air  from  the  forward  edge 
of  every  portion  of  the  blade,  and  to  set  every  portion  or 
face  of  the  blade  at  such  an  angle  that  the  forward  edge 
at  every  point  would  "  cut  under  "  the  air  rather  than 
move  it  laterally  or  carry  it  with  the  wheel,  and  that 
while  portions  of  the  blade  might  be  so  bent  as  to  throw 
the  air  outward,  other  portions,  if  not  properly  shaped, 
would  draw  it  back,  creating  counter  currents.  I  found 
that  to  prevent  such  results  it  was  essential  to  vary  the 
angle  and  curve  of  the  blade  at  different  points,  and  that 
although  such  angles  and  curves  would  be  different,  ac- 
cording to  the  sizes  of  the  wheels  and  number  of  blades, 
there  were  certain  definite  and  specific  proportions  and 
forms  common  to  all,  which  result  in  much  improved 
effects,  and  which  I  will  now  specify. 

The  hub  A  of  the  wheel  may  be  solid,  or  may  consist 
of  disks  a  a'  secured  to  the  shaft  B.  From  the  hub  ex- 


172  VENTILATION  AND  WARMING  OF  SCHOOL-BUILDINGS. 

tend  radial  ribs  b,  which  meet  an  annular  rim  c,  and 
said  ribs  constitute  the  straight  edges  of  the  blade  D,  the 
rim  c  and  ribs  being  all  in  the  same  vertical  plane  x.  The 
diameter  of  the  hub  A  and  the  depth  of  the  wheel  should, 
to  secure  the  best  results,  be  about  equal  to  one  sixth  of 
the  diameter  of  the  wheel,  and  the  ribs  or  edges  b,  instead 
of  being  radial,  should  coincide  with  lines  extending  from 
the  periphery,  through  the  hub,  midway  between  the  axis 
and  periphery  of  the  latter.  The  blades,  instead  of  being 
set  with  their  inner  ends  parallel  to  the  axis,  join  the  hub 
upon  lines  y  y,  crossing  the  axial  line  at  an  angle  at  the 
center,  and  the  forward  edge  of  each  blade  corresponds  to 
a  curve  which  is  gradually  increased  toward  the  outer 
end,  the  edges  of  all  the  blades  being  upon  a  plane  z  z, 
parallel  to  the  plane  x  x.  Thus  the  forward  edge  of  each 
blade  may  be  a  rib,  e,  extending  from  the  hub  nearly  par- 
allel for  a  short  distance  with  the  rib  b,  and  then  curved 
forward  until  it  nears  the  periphery,  when  the  curve  is 
sharper,  as  shown.  The  body  of  the  blade,  between  the 
edges  or  ribs  b,  e,  is  gradually  bent  at  an  angle  which  be- 
comes more  and  more  obtuse  to  the  axis  of  the  shaft  as  it 
approaches  the  periphery,  as  shown  in  fine  lines,  Fig.  C, 
and  is  also  bent  from  a  perpendicular  line,  parallel  to  the 
edge  5,  as  it  recedes  from  said  line  toward  the  edge  e,  as 
shown  in  dotted  lines,  Fig.  A.  At  the  periphery  the 
blade  is  bent  to  form  a  peripheral  section,  d,  that  extends 
from  the  blade  to  the  rim  c,  and  has  a  forward  edge,  t, 
parallel  to  the  axis  of  the  shaft.  This  peripheral  section 
may  form  part  of  the  blade,  or  may  be  a  separate  piece 
riveted  or  otherwise  secured  thereto.  If  the  blade  were 
bent  or  hollowed  from  each  end  to  the  center,  as  shown 
by  the  outline,  Fig.  D,  the  air  collected  by  the  ends  of 
the  blade,  instead  of  being  carried  outward,  would  be 
drawn  to  the  center  and  thrown  backward  in  currents, 


APPENDIX  F.  173 

interfering  with  the  flow  of  air  to  the  wheel ;  so,  if  the 
blade  at  any  point,  as  at  the  hub,  Fig.  E,  is  too  nearly 
parallel  with  the  axis  of  the  shaft,  the  air,  instead  of  be- 
ing sent  forward,  will  be  carried  round  with  the  wheel, 
and  the  effect  will  not  be  proportioned  to  the  power  ex- 
pended. By  setting  the  blade  at  an  angle  to  the  axis,  as 
shown  in  Fig.  C,  by  maintaining  the  portion  near  the 
hub  comparatively  flat,  by  bending  the  body  beyond  the 
center,  and  by  giving  a  sharper  curve  thereto  near  the 
periphery,  where  it  meets  the  peripheral  section,  as  de- 
scribed, I  have  succeeded  in  preventing  any  back-flow, 
and  have  with  comparatively  little  power  imparted  move- 
ment to  large  volumes  of  air  in  one  direction,  and  in 
nearly  solid  columns.  This  effect  is  increased  by  setting 
the  blade  somewhat  tangential  to  the  axis,  as  described, 
instead  of  radially,  the  outer  end  thus  being  pitched  for- 
ward, so  as  to  draw  in  the  air,  instead  of  dispersing  it 
radially.  This  will  be  best  understood  on  reference  to 
diagrams  Figs.  F  and  G,  in  which  diagram  F  illustrates 
a  radial  blade  which  throws  out  the  air  by  its  revolution, 
while  diagram  G  represents  a  blade  set  tangentially  to 
the  hub,  and  tending  to  draw  the  air  toward  the  latter. 
It  will  be  evident  that  the  ribs  b  e  may  be  flanges  formed 
by  bending  the  edges  of  the  blades. 

It  is  common  to  set  ventilating-fans  in  openings  in 
walls  or  frames,  which  completely  surround  the  periph- 
eries of  the  fans  and  prevent  any  radial  inflow  of  air.  I 
set  my  fan  back  so  that  the  front  face  will  be  nearly  on  the 
same  plane  as  the  inner  surface,  w,  of  the  wall  or  frame, 
as  shown,  thus  permitting  a  free  flow  of  air  to  the  pe- 
riphery (see  Fig.  13). 

THE   END. 


BOOKS  FOR  TEACHERS. 

Spencer's  Education : 

INTELLECTUAL,  MORAL,  AND  PHYSICAL.  Divided  into  four  chap- 
ters: What  Knowledge  ia  of  most  Worth  ?— Intellectual  Education— Moral 
Education— Physical  Education.  Price,  §1.23. 

Bain's  Education  as  a  Science. 

The  author  views  the  "  teaching  art "  from  a  fcientiflc  point  of  view,  and 
tests  ordinary  experiences  by  bringing  them  to  the  criterion  of  psychological 
law.  Price,  §1.75. 

Bain's  On  Teaching  English, 

WITH  DETAILED  EXAMPLES,  AND  AN  INQUIRY  INTO  THE  DEFI- 
NITION OF  POETRY.  Price,  $1.25. 

Johonnot's  Principles  and  Practice  of  Teaching. 

This  is  a  practical  book  by  an  experienced  teacher.  The  subject  of  education 
is  treated  in  a  systematic  and  comprehensive  manner,  and  shows  how  rational 
processes  may  be  substituted  for  school-room  routine.  Price,  $1.60. 

Baldwin's  Art  of  School  Management. 

This  is  a  very  helpful  hand-book  for  the  teacher.  He  will  find  it  full  of  prac- 
tical suggestions  in  regard  to  all  the  details  of  school-room  work,  and  how  to 
manage  it  to  best  advantage.  Price,  $1.50. 

Greenwood's  Principles  of  Education  Practically  Applied. 

The  object  of  this  work  throughout  is  to  impress  this  important  question 
upon  the  mind  of  the  teacher:  •'  How  ghaU  I  teach  so  as  to  have  my pupilg 
become  self-reliant,  independent,  manly  men  and  womanly  women  f"  Price, 
$1.00. 

Sully's  Outlines  of  Psychology, 

WITH  SPECIAL  REFERENCE  TO  THE  THEORY  OF  EDUCATION. 
Price,  $3.00. 

Sully's  Hand-Book  of  Psychology, 

ON  THE  BASIS  OF  OUTLINES  OF  PSYCHOLOGY.  A  practical  exposi- 
tion of  the  elements  of  Mental  Science,  with  special  applications  to  the  Art 
of  Teaching,  designed  for  the  use  of  Schools,  Teachers,  Reading  Circles,  and 
Students  generally.  Price,  $1.50. 

.  Bain's  Moral  Science. 

A  COMPENDIUM  OF  ETHICS.  Divided  into  two  divisions.  The  first— 
the  Theory  of  Ethics — treats  at  length  of  the  two  great  questions,  the  ethical 
standard  and  the  moral  faculty ;  the  second  division— on  the  Ethical  Systems 
— is  a  full  detail  of  all  the  systems,  ancient  and  modern,  by  conjoined  abstract 
and  summary.  Price,  $1.50. 

McArthur's  Education, 

IN  ITS  RELATION  TO  MANUAL  INDUSTRY.  Tho  important  subject 
of  manual  education  is  thoroughly  and  clearly  treated.  Price,  $1.50. 

Hodgson's  Errors  in  the  Use  of  English. 

A  work  for  the  teacher's  table,  and  invaluable  for  classes  in  grammar  and 
literature.  Price,  $1.50. 

Descriptive  Catalogue  sent  free  on  application.    Special  prices  will  be  made  on 

D.  APPLETON  &  CO.,  Publishers, 
New  York,  Boston,  Chicugo,  Atlanta,  San  Francisco- 


A   NEW  AND  CAREFULLY  REVISED  EDITION  OF 

JOHN   STUART  MILL'S 


Abridged,  with  Critical,  Bibliographical,  and  Explana- 
tory Notes,  and  a  Sketch  of  the  History 
of  Political  Economy. 

By  JAMES  LAURENCE  LAUGHLIN,  Ph.  D., 

Assistant  Professor  of  Political  Economy  in  Harvard  University. 


With  Twenty-four  Maps  and  Charts.    8vo.    658  pages. 
Cloth,  $3.50. 


No  writer  on  Political  Economy,  since  Adam  Smith,  the  acknowledged 
father  of  Political  Science,  can  be  compared  in  originalitv,  exact  and  forcible 
expression,  and  apt  illustration,  to  John  Stuart  Mill.  His  writings  on  this 
great  subject,  while  practical  and  popular  in  their  adaptation,  are  also 
characterized  by  the  true  philosophic  method.  In  his  knowledge  of  facts 
and  conditions,  his  clearness  of  understanding,  and  the  soundness  of  his 
reasoning,  he  excels  all  other  writers  on  the  subject,  and  his  "  PRINCIPLES 
OF  POLITICAL  ECONOMY"  has  been  an  unfailing 'source  of  information  and 
authority  to  all  subsequent  writers  and  students  of  political  science. 

To  present  this  work  in  form,  size,  and  method,  somewhat  better  adapted 
to  class-room  use,  and  present  modes  of  study,  and  at  the  same  time  to 

E reserve  it  so  far  as  possible  in  the  form  and  language  of  its  great  author, 
as  been  the  aim  in  the  present  revision.  The  editor  has  made  this  work 
essentially  a  revision,  and  not  a  systematic  mutilation.  The  publishers 
therefore  feel  confident  that  the  new  edition  will  be  found  thoroughly 
adapted  to  class  use,  and  as  such  will  prove  a  valuable  and  satisfactory  text- 
book, and  at  the  same  time  will  be  found  to  retain  and  present  all  the 
essential  and  valuable  features  of  the  original  work. 

The  new  edition  retains,  in  its  own  clear  exposition,  the  connected  sys- 
tem of  the  original,  and  at  the  same  time  its  size  is  lessened  by  omitting 
what  is  Sociology  rather  than  Political  Economy.  The  difficulties  of  the 
more  abstract  portions  of  the  original  work  are  much  lightened,  and  the 
new  edition  presents,  in  connection  with  the  general  tenor  of  the  work, 
some  important  additions  of  later  writers. 


For  sale  by  all  booksellers  ;  or  sent  by  mail,  post-paid,  on  receipt  of  price. 


New  York:  D.  APPLETON  &  CO.,  Publishers,  1,  3,  &  5  Bond  Street. 


EDUCATION   IN   RELATION   TO 
MANUAL  INDUSTRY. 

By  ARTHUR  MACARTHUR,  LL.  D.      I2mo.      Cloth,  $1.50. 

"  Mr.  Mac  Arthur's  able  treatise  is  designed  to  adapt  to  the  nsnal  methods  of 
instruction  a  system  of  rudimental  science  and  manual  art.  He  describes  the 
progress  of  industrial  education  in  France,  Belgium,  Russia,  Germany, and  Great 
Britain,  and  the  establishment  of  their  professional  schools.  The  technical 
schools  of  the  United  States  are  next  reviewed.  Mr.  MacArthur  is  anxious  that 
the  State  governments  should  take  up  the  subject,  and  enable  every  girl  and  boy 
to  receive  a  practical  education  which  would  fit  them  for  use  In  this  world.  This 
valuable  book  should  be  carefully  read  and  meditated  upon.  The  discussion  is 
of  high  importance."— Philadelphia  Public  Ledger. 

"The  importance  of  this  book  caji  not  be  too  greatly  urged.  It  gives  a 
statistical  account  of  the  industries  of  various  countries,  the  number  of  workmen 
and  workwomen,  and  the  degree  of  perfection  attained.  America  is  behind  in 
native  production,  and,  when  we  read  of  the  importation  of  foreign  workmen  in 
simple  manufacture  such  as  glass,  it  is  a  stimulus  for  young  men  to  train  them- 
selves early  as  is  done  in  foreign  countries.  The  necessity  of  training-schools 
and  the  value  and  dignity  of  trades  are  made  evident  in  this  work.  It  is  particu- 
larly helpful  to  women,  as  it  mentions  the  variety  of  employments  which  they 
can  practice,  and  gives  the  success  already  reached  by  them.  It  serves  as  a  his- 
tory and  encyclopaedia  of  facts  relating  to  industries,  and  is  very  well  written."— 
Boston  Globe. 

"The  advocates  of  industrial  education  in  schools  will  find  a  very  complete 
manual  of  the  whole  subject  in  Mr.  MacArthur's  book."— Springfield  Republican. 

"  A  sensible  and  much-needed  plea  for  the  establishment  of  schools  for  indus- 
try by  the  state,  supported  by  the  practical  illustration  of  what  has  been  accom- 
plished for  the  good  of  the  state  by  such  schools  in  foreign  countries.  Great 
Britain  has  never  regretted  the  step  she  took  when,  recognizing  at  the  Crystal 
Palace  Exhibition  her  inferiority  in  industrial  art-work,  she  at  once  established 
the  South  Kensington  Museum,  with  its  annexed  art-schools,  at  a  cost  of  six  mill- 
ion dollars."-  The  Critic. 

"The  aim  of  the  book  is  succinctly  stated,  as  it  ought  to  be,  in  the  preface : 
'What  is  industrial  education  ?  What  are  its  merits  and  objects,  and,  above  all. 
what  power  does  it  possess  of  ministering  to  some  useful  purpose  in  the  practical 
arts  of  lire?'  These  are  questions  about  which  we  are  deeply  concerned  in  this 
country,  and  the  author  has  essayed  to  answer  them,  not  by  an  abstract  discus- 
sion of  technical  instruction,  but  by  giving  a  full  and  accurate  account  of  the 
experiments  in  industrial  training  which  have  been  actually  and  successfully 
carried  out  in  Europe." — New  York  Sun. 

"A  most  interesting  and  suggestive  work  on  a  matter  of  immediate  and 
universal  Importance." — New  York  Daily  Graphic. 

"An  admirable  book  on  a  much-neglected  subject.  Those  countries  have 
made  the  roost  rapid  advance  in  the  line  of  new  industries  which  have  paid  the 
most  attention  to  the  methods  here  recommended  of  primary  instruction.  The 
land  that  neglects  them  will  sooner  or  later  cease  to  be  in  the  front  ranks  of 
applied  science  and  the  useful  arts." — New  York  Journal  of  Commerce. 


For  salt  by  all  booksellers  ;  or  sent  by  mail,  post-paid,  on  receipt  of  price. 


New  York:  D.  APPLETON  &  CO..  1.  3.  &  5  Bond  Street 


SULLY'S  TWO  GREAT  WORKS. 


Outlines  of  Psychology,  with  Special  Reference 
to  the  Theory  of  Education. 

A  Text-Book  for  Colleges.  By  JAMES  SULLY,  A.M.,  Ex- 
aminer for  the  Moral  Sciences  Tripos  in  the  University  of 
Cambridge,  etc.,  etc. 

"  A  book  that  has  been  long  wanted  by  all  who  are  engaged  in  the 
Business  of  teaching  and  desire  to  master  its  principles.  In  the  first 
place,  it  is  an  elaborate  treatise  on  the  human  mind,  of  independent 
merit  as  representing  the  latest  and  best  work  of  all  schools  of  psycho- 
logical inquiry.  But  of  equal  importance,  and  what  will  be  prized  as  a 
new  and  most  desirable  feature  of  a  work  on  mental  science,  are  the 
educational  applications  that  are  made  throughout  in  separate  text  and 
type,  so  that,  with  the  explication  of  mental  phenomena,  there  comes  at 
once  the  application  to  the  art  of  education." 

Crown  8vo.     Price,  $3.00. 


Teacher's  Hand-Book  of  Psychology. 

On  the  Basis  of   "Outlines  of  Psychology."      By  JAMES 
SULLY,  M.  A. 

A  practical  exposition  of  the  elements  of  Mental  Science,  with  spe- 
cial applications  to  the  Art  of  Teaching,  designed  for  the  use  of  Schools, 
Teachers,  Reading  Circles,  and  Students  generally.  This  book  is  not  a 
mere  abridgment  of  the  author's  "Outlines,"  but  has  been  mainly  re- 
written for  a  more  direct  educational  purpose,  and  is  essentially  a  new 
work.  It  has  been  heretofore  announced  as  "  Elements  of  Psychology." 

NOTE. — No  American  abridgments  or  editions  of  Mr.  Sultys  works 
tre  authorized  except  those  published  by  the  undersigned. 

12mo,  414  pages.     Price,  $1.50. 

D.  APPLETON  &  CO.,  PUBLISHERS, 
New  York,  Boston,  Chicago,  Atlanta,  San  Francisco. 


THE  LIBRARY 
UNIVERSITY  OF  CALIFORNIA 

Santa  Barbara 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW. 


Series  9482 


